php链式操作mysql数据库的方法是什么

本篇内容介绍了“PHP链式操作mysql数据库的方法是什么”的有关知识，在实际案例的操作过程中，不少人都会遇到这样的困境，接下来就让小编带领大家学习一下如何处理这些情况吧！希望大家仔细阅读，能够学有所成！

封装类常用操作使用示例

// 初始化db连接$db = new \Workerman\Mysql\Connection('host', 'port', 'user', 'passWord', 'db_name');// 获取所有数据$db->select('ID,Sex')->from('Persons')->where('sex= :sex AND ID = :id')->bindValues(array('sex'=>'M', 'id' => 1))->query();//等价于$db->select('ID,Sex')->from('Persons')->where("sex= 'M' AND ID = 1")->query();//等价于$db->query("SELECT ID,Sex FROM `Persons` WHERE sex='M' AND ID = 1");// 获取一行数据$db->select('ID,Sex')->from('Persons')->where('sex= :sex')->bindValues(array('sex'=>'M'))->row();//等价于$db->select('ID,Sex')->from('Persons')->where("sex= 'M' ")->row();//等价于$db->row("SELECT ID,Sex FROM `Persons` WHERE sex='M'");// 获取一列数据$db->select('ID')->from('Persons')->where('sex= :sex')->bindValues(array('sex'=>'M'))->column();//等价于$db->select('ID')->from('Persons')->where("sex= 'F' ")->column();//等价于$db->column("SELECT `ID` FROM `Persons` WHERE sex='M'");// 获取单个值$db->select('ID')->from('Persons')->where('sex= :sex')->bindValues(array('sex'=>'M'))->single();//等价于$db->select('ID')->from('Persons')->where("sex= 'F' ")->single();//等价于$db->single("SELECT ID FROM `Persons` WHERE sex='M'");// 复杂查询$db->select('*')->from('table1')->innerJoin('table2','table1.uid = table2.uid')->where('age > :age')->groupBy(array('aid'))->having('foo="foo"')->orderByASC(array('did'))->limit(10)->offset(20)->bindValues(array('age' => 13));// 等价于$db->query('SELECT * FROM `table1` INNER JOIN `table2` ON `table1`.`uid` = `table2`.`uid`WHERE age > 13 GROUP BY aid HAVING foo="foo" ORDER BY did LIMIT 10 OFFSET 20');// 插入$insert_id = $db->insert('Persons')->cols(array(    'Firstname'=>'abc',    'Lastname'=>'efg',    'Sex'=>'M',    'Age'=>13))->query();等价于$insert_id = $db->query("INSERT INTO `Persons` ( `Firstname`,`Lastname`,`Sex`,`Age`)VALUES ( 'abc', 'efg', 'M', 13)");// 更新$row_count = $db->update('Persons')->cols(array('sex'))->where('ID=1')->bindValue('sex', 'F')->query();// 等价于$row_count = $db->update('Persons')->cols(array('sex'=>'F'))->where('ID=1')->query();// 等价于$row_count = $db->query("UPDATE `Persons` SET `sex` = 'F' WHERE ID=1");// 删除$row_count = $db->delete('Persons')->where('ID=9')->query();// 等价于$row_count = $db->query("DELETE FROM `Persons` WHERE ID=9");// 事务$db->beginTrans();....$db->commitTrans(); // or $db->rollBackTrans();

封装源码（保存文件引用）

<?phpclass Connection{        protected $uNIOn = array();        protected $for_update = false;        protected $cols = array();        protected $from = array();        protected $from_key = -1;        protected $group_by = array();        protected $having = array();        protected $bind_having = array();        protected $paging = 10;        protected $bind_values = array();        protected $where = array();        protected $bind_where = array();        protected $order_by = array();        protected $order_asc = true;        protected $limit = 0;        protected $offset = 0;        protected $flags = array();        protected $table;        protected $last_insert_id_names = array();        protected $col_values;        protected $returning = array();        protected $type = '';        protected $pdo;        protected $sQuery;        protected $settings = array();        protected $parameters = array();        protected $lastsql = '';        protected $success = false;        public function select($cols = '*')    {        $this->type = 'SELECT';        if (!is_array($cols)) {            $cols = explode(',', $cols);        }        $this->cols($cols);        return $this;    }        public function delete($table)    {        $this->type  = 'DELETE';        $this->table = $this->quoteName($table);        $this->fromRaw($this->quoteName($table));        return $this;    }        public function update($table)    {        $this->type  = 'UPDATE';        $this->table = $this->quoteName($table);        return $this;    }        public function insert($table)    {        $this->type  = 'INSERT';        $this->table = $this->quoteName($table);        return $this;    }        public function calcFoundRows($enable = true)    {        $this->setFlag('SQL_CALC_FOUND_ROWS', $enable);        return $this;    }        public function cache($enable = true)    {        $this->setFlag('SQL_CACHE', $enable);        return $this;    }        public function noCache($enable = true)    {        $this->setFlag('SQL_NO_CACHE', $enable);        return $this;    }        public function straightJoin($enable = true)    {        $this->setFlag('STRAIGHT_JOIN', $enable);        return $this;    }        public function highPriority($enable = true)    {        $this->setFlag('HIGH_PRIORITY', $enable);        return $this;    }        public function smallResult($enable = true)    {        $this->setFlag('SQL_SMALL_RESULT', $enable);        return $this;    }        public function bigResult($enable = true)    {        $this->setFlag('SQL_BIG_RESULT', $enable);        return $this;    }        public function bufferResult($enable = true)    {        $this->setFlag('SQL_BUFFER_RESULT', $enable);        return $this;    }        public function forUpdate($enable = true)    {        $this->for_update = (bool)$enable;        return $this;    }        public function distinct($enable = true)    {        $this->setFlag('DISTINCT', $enable);        return $this;    }        public function lowPriority($enable = true)    {        $this->setFlag('LOW_PRIORITY', $enable);        return $this;    }        public function ignore($enable = true)    {        $this->setFlag('IGNORE', $enable);        return $this;    }        public function quick($enable = true)    {        $this->setFlag('QUICK', $enable);        return $this;    }        public function delayed($enable = true)    {        $this->setFlag('DELAYED', $enable);        return $this;    }        public function __toString()    {        $union = '';        if ($this->union) {            $union = implode(' ', $this->union) . ' ';        }        return $union . $this->build();    }        public function setPaging($paging)    {        $this->paging = (int)$paging;        return $this;    }        public function getPaging()    {        return $this->paging;    }        public function getBindValues()    {        switch ($this->type) {            case 'SELECT':                return $this->getBindValuesSELECT();            case 'DELETE':            case 'UPDATE':            case 'INSERT':                return $this->getBindValuesCOMMON();            default :                throw new Exception("type err");        }    }        public function getBindValuesSELECT()    {        $bind_values = $this->bind_values;        $i           = 1;        foreach ($this->bind_where as $val) {            $bind_values[$i] = $val;            $i++;        }        foreach ($this->bind_having as $val) {            $bind_values[$i] = $val;            $i++;        }        return $bind_values;    }        protected function addColSELECT($key, $val)    {        if (is_string($key)) {            $this->cols[$val] = $key;        } else {            $this->addColWithAlias($val);        }    }        protected function addColWithAlias($spec)    {        $parts = explode(' ', $spec);        $count = count($parts);        if ($count == 2 && trim($parts[0]) != '' && trim($parts[1]) != '') {            $this->cols[$parts[1]] = $parts[0];        } elseif ($count == 3 && strtoupper($parts[1]) == 'AS') {            $this->cols[$parts[2]] = $parts[0];        } else {            $this->cols[] = trim($spec);        }    }        public function from($table)    {        return $this->fromRaw($this->quoteName($table));    }        public function fromRaw($table)    {        $this->from[] = array($table);        $this->from_key++;        return $this;    }        public function fromSubSelect($table, $name)    {        $this->from[] = array("($table) AS " . $this->quoteName($name));        $this->from_key++;        return $this;    }        public function join($table, $cond = null, $type = '')    {        return $this->joinInternal($type, $table, $cond);    }        protected function joinInternal($join, $table, $cond = null)    {        if (!$this->from) {            throw new Exception('Cannot join() without from()');        }        $join                          = strtoupper(ltrim("$join JOIN"));        $table                         = $this->quoteName($table);        $cond                          = $this->fixJoinCondition($cond);        $this->from[$this->from_key][] = rtrim("$join $table $cond");        return $this;    }        protected function fixJoinCondition($cond)    {        if (!$cond) {            return '';        }        $cond = $this->quoteNamesIn($cond);        if (strtoupper(substr(ltrim($cond), 0, 3)) == 'ON ') {            return $cond;        }        if (strtoupper(substr(ltrim($cond), 0, 6)) == 'USING ') {            return $cond;        }        return 'ON ' . $cond;    }        public function innerJoin($table, $cond = null)    {        return $this->joinInternal('INNER', $table, $cond);    }        public function leftJoin($table, $cond = null)    {        return $this->joinInternal('LEFT', $table, $cond);    }        public function rightJoin($table, $cond = null)    {        return $this->joinInternal('RIGHT', $table, $cond);    }        public function joinSubSelect($join, $spec, $name, $cond = null)    {        if (!$this->from) {            throw new \Exception('Cannot join() without from() first.');        }        $join                          = strtoupper(ltrim("$join JOIN"));        $name                          = $this->quoteName($name);        $cond                          = $this->fixJoinCondition($cond);        $this->from[$this->from_key][] = rtrim("$join ($spec) AS $name $cond");        return $this;    }        public function groupBy(array $cols)    {        foreach ($cols as $col) {            $this->group_by[] = $this->quoteNamesIn($col);        }        return $this;    }        public function having($cond)    {        $this->addClauseCondWithBind('having', 'AND', func_get_args());        return $this;    }        public function orHaving($cond)    {        $this->addClauseCondWithBind('having', 'OR', func_get_args());        return $this;    }        public function page($page)    {        $this->limit  = 0;        $this->offset = 0;        $page = (int)$page;        if ($page > 0) {            $this->limit  = $this->paging;            $this->offset = $this->paging * ($page - 1);        }        return $this;    }        public function union()    {        $this->union[] = $this->build() . ' UNION';        $this->reset();        return $this;    }        public function unionAll()    {        $this->union[] = $this->build() . ' UNION ALL';        $this->reset();        return $this;    }        protected function reset()    {        $this->resetFlags();        $this->cols       = array();        $this->from       = array();        $this->from_key   = -1;        $this->where      = array();        $this->group_by   = array();        $this->having     = array();        $this->order_by   = array();        $this->limit      = 0;        $this->offset     = 0;        $this->for_update = false;    }        protected function resetAll()    {        $this->union                = array();        $this->for_update           = false;        $this->cols                 = array();        $this->from                 = array();        $this->from_key             = -1;        $this->group_by             = array();        $this->having               = array();        $this->bind_having          = array();        $this->paging               = 10;        $this->bind_values          = array();        $this->where                = array();        $this->bind_where           = array();        $this->order_by             = array();        $this->limit                = 0;        $this->offset               = 0;        $this->flags                = array();        $this->table                = '';        $this->last_insert_id_names = array();        $this->col_values           = array();        $this->returning            = array();        $this->parameters           = array();    }        protected function buildSELECT()    {        return 'SELECT'            . $this->buildFlags()            . $this->buildCols()            . $this->buildFrom()            . $this->buildWhere()            . $this->buildGroupBy()            . $this->buildHaving()            . $this->buildOrderBy()            . $this->buildLimit()            . $this->buildForUpdate();    }        protected function buildDELETE()    {        return 'DELETE'            . $this->buildFlags()            . $this->buildFrom()            . $this->buildWhere()            . $this->buildOrderBy()            . $this->buildLimit()            . $this->buildReturning();    }        protected function buildCols()    {        if (!$this->cols) {            throw new Exception('No columns in the SELECT.');        }        $cols = array();        foreach ($this->cols as $key => $val) {            if (is_int($key)) {                $cols[] = $this->quoteNamesIn($val);            } else {                $cols[] = $this->quoteNamesIn("$val AS $key");            }        }        return $this->indentCsv($cols);    }        protected function buildFrom()    {        if (!$this->from) {            return '';        }        $refs = array();        foreach ($this->from as $from) {            $refs[] = implode(' ', $from);        }        return ' FROM' . $this->indentCsv($refs);    }        protected function buildGroupBy()    {        if (!$this->group_by) {            return '';        }        return ' GROUP BY' . $this->indentCsv($this->group_by);    }        protected function buildHaving()    {        if (!$this->having) {            return '';        }        return ' HAVING' . $this->indent($this->having);    }        protected function buildForUpdate()    {        if (!$this->for_update) {            return '';        }        return ' FOR UPDATE';    }        public function where($cond)    {        if (is_array($cond)) {            foreach ($cond as $key => $val) {                if (is_string($key)) {                    $this->addWhere('AND', array($key, $val));                } else {                    $this->addWhere('AND', array($val));                }            }        } else {            $this->addWhere('AND', func_get_args());        }        return $this;    }        public function orWhere($cond)    {        if (is_array($cond)) {            foreach ($cond as $key => $val) {                if (is_string($key)) {                    $this->addWhere('OR', array($key, $val));                } else {                    $this->addWhere('OR', array($val));                }            }        } else {            $this->addWhere('OR', func_get_args());        }        return $this;    }        public function limit($limit)    {        $this->limit = (int)$limit;        return $this;    }        public function offset($offset)    {        $this->offset = (int)$offset;        return $this;    }        public function orderBy(array $cols)    {        return $this->addOrderBy($cols);    }        public function orderByASC(array $cols, $order_asc = true)    {        $this->order_asc = $order_asc;        return $this->addOrderBy($cols);    }        public function orderByDESC(array $cols)    {        $this->order_asc = false;        return $this->addOrderBy($cols);    }    // -------------abstractquery----------        protected function indentCsv(array $list)    {        return ' ' . implode(',', $list);    }        protected function indent(array $list)    {        return ' ' . implode(' ', $list);    }        public function bindValues(array $bind_values)    {        foreach ($bind_values as $key => $val) {            $this->bindValue($key, $val);        }        return $this;    }        public function bindValue($name, $value)    {        $this->bind_values[$name] = $value;        return $this;    }        protected function buildFlags()    {        if (!$this->flags) {            return '';        }        return ' ' . implode(' ', array_keys($this->flags));    }        protected function setFlag($flag, $enable = true)    {        if ($enable) {            $this->flags[$flag] = true;        } else {            unset($this->flags[$flag]);        }    }        protected function resetFlags()    {        $this->flags = array();    }        protected function addWhere($andor, $conditions)    {        $this->addClauseCondWithBind('where', $andor, $conditions);        return $this;    }        protected function addClauseCondWithBind($clause, $andor, $conditions)    {        $cond = array_shift($conditions);        $cond = $this->quoteNamesIn($cond);        $bind =& $this->{"bind_{$clause}"};        foreach ($conditions as $value) {            $bind[] = $value;        }        $clause =& $this->$clause;        if ($clause) {            $clause[] = "$andor $cond";        } else {            $clause[] = $cond;        }    }        protected function buildWhere()    {        if (!$this->where) {            return '';        }        return ' WHERE' . $this->indent($this->where);    }        protected function addOrderBy(array $spec)    {        foreach ($spec as $col) {            $this->order_by[] = $this->quoteNamesIn($col);        }        return $this;    }        protected function buildOrderBy()    {        if (!$this->order_by) {            return '';        }        if ($this->order_asc) {            return ' ORDER BY' . $this->indentCsv($this->order_by) . ' ASC';        } else {            return ' ORDER BY' . $this->indentCsv($this->order_by) . ' DESC';        }    }        protected function buildLimit()    {        $has_limit  = $this->type == 'DELETE' || $this->type == 'UPDATE';        $has_offset = $this->type == 'SELECT';        if ($has_offset && $this->limit) {            $clause = " LIMIT {$this->limit}";            if ($this->offset) {                $clause .= " OFFSET {$this->offset}";            }            return $clause;        } elseif ($has_limit && $this->limit) {            return " LIMIT {$this->limit}";        }        return '';    }        public function quoteName($spec)    {        $spec = trim($spec);        $seps = array(' AS ', ' ', '.');        foreach ($seps as $sep) {            $pos = strripos($spec, $sep);            if ($pos) {                return $this->quoteNameWithSeparator($spec, $sep, $pos);            }        }        return $this->replaceName($spec);    }        protected function quoteNameWithSeparator($spec, $sep, $pos)    {        $len   = strlen($sep);        $part1 = $this->quoteName(substr($spec, 0, $pos));        $part2 = $this->replaceName(substr($spec, $pos + $len));        return "{$part1}{$sep}{$part2}";    }        public function quoteNamesIn($text)    {        $list = $this->getListForQuoteNamesIn($text);        $last = count($list) - 1;        $text = null;        foreach ($list as $key => $val) {            if (($key + 1) % 3) {                $text .= $this->quoteNamesInLoop($val, $key == $last);            }        }        return $text;    }        protected function getListForQuoteNamesIn($text)    {        $apos = "'";        $quot = '"';        return preg_split(            "/(($apos+|$quot+|\\$apos+|\\$quot+).*?\\2)/",            $text,            -1,            PREG_SPLIT_DELIM_CAPTURE        );    }        protected function quoteNamesInLoop($val, $is_last)    {        if ($is_last) {            return $this->replaceNamesAndAliasIn($val);        }        return $this->replaceNamesIn($val);    }        protected function replaceNamesAndAliasIn($val)    {        $quoted = $this->replaceNamesIn($val);        $pos    = strripos($quoted, ' AS ');        if ($pos !== false) {            $bracket = strripos($quoted, ')');            if ($bracket === false) {                $alias = $this->replaceName(substr($quoted, $pos + 4));                $quoted = substr($quoted, 0, $pos) . " AS $alias";            }        }        return $quoted;    }        protected function replaceName($name)    {        $name = trim($name);        if ($name == '*') {            return $name;        }        return '`' . $name . '`';    }        protected function replaceNamesIn($text)    {        $is_string_literal = strpos($text, "'") !== false            || strpos($text, '"') !== false;        if ($is_string_literal) {            return $text;        }        $word = '[a-z_][a-z0-9_]*';        $find = "/(\\b)($word)\\.($word)(\\b)/i";        $repl = '$1`$2`.`$3`$4';        $text = preg_replace($find, $repl, $text);        return $text;    }    // ---------- insert --------------        public function setLastInsertIdNames(array $last_insert_id_names)    {        $this->last_insert_id_names = $last_insert_id_names;    }        public function into($table)    {        $this->table = $this->quoteName($table);        return $this;    }        protected function buildINSERT()    {        return 'INSERT'            . $this->buildFlags()            . $this->buildInto()            . $this->buildValuesForInsert()            . $this->buildReturning();    }        protected function buildInto()    {        return " INTO " . $this->table;    }        public function getLastInsertIdName($col)    {        $key = str_replace('`', '', $this->table) . '.' . $col;        if (isset($this->last_insert_id_names[$key])) {            return $this->last_insert_id_names[$key];        }        return null;    }        public function col($col)    {        return call_user_func_array(array($this, 'addCol'), func_get_args());    }        public function cols(array $cols)    {        if ($this->type == 'SELECT') {            foreach ($cols as $key => $val) {                $this->addColSELECT($key, $val);            }            return $this;        }        return $this->addCols($cols);    }        public function set($col, $value)    {        return $this->setCol($col, $value);    }        protected function buildValuesForInsert()    {        return ' (' . $this->indentCsv(array_keys($this->col_values)) . ') VALUES (' .            $this->indentCsv(array_values($this->col_values)) . ')';    }    // ------update-------        public function table($table)    {        $this->table = $this->quoteName($table);        return $this;    }        protected function build()    {        switch ($this->type) {            case 'DELETE':                return $this->buildDELETE();            case 'INSERT':                return $this->buildINSERT();            case 'UPDATE':                return $this->buildUPDATE();            case 'SELECT':                return $this->buildSELECT();        }        throw new Exception("type empty");    }        protected function buildUPDATE()    {        return 'UPDATE'            . $this->buildFlags()            . $this->buildTable()            . $this->buildValuesForUpdate()            . $this->buildWhere()            . $this->buildOrderBy()            . $this->buildLimit()            . $this->buildReturning();    }        protected function buildTable()    {        return " {$this->table}";    }        protected function buildValuesForUpdate()    {        $values = array();        foreach ($this->col_values as $col => $value) {            $values[] = "{$col} = {$value}";        }        return ' SET' . $this->indentCsv($values);    }    // ----------Dml---------------        public function getBindValuesCOMMON()    {        $bind_values = $this->bind_values;        $i           = 1;        foreach ($this->bind_where as $val) {            $bind_values[$i] = $val;            $i++;        }        return $bind_values;    }        protected function addCol($col)    {        $key                    = $this->quoteName($col);        $this->col_values[$key] = ":$col";        $args                   = func_get_args();        if (count($args) > 1) {            $this->bindValue($col, $args[1]);        }        return $this;    }        protected function addCols(array $cols)    {        foreach ($cols as $key => $val) {            if (is_int($key)) {                $this->addCol($val);            } else {                $this->addCol($key, $val);            }        }        return $this;    }        protected function setCol($col, $value)    {        if ($value === null) {            $value = 'NULL';        }        $key                    = $this->quoteName($col);        $value                  = $this->quoteNamesIn($value);        $this->col_values[$key] = $value;        return $this;    }        protected function addReturning(array $cols)    {        foreach ($cols as $col) {            $this->returning[] = $this->quoteNamesIn($col);        }        return $this;    }        protected function buildReturning()    {        if (!$this->returning) {            return '';        }        return ' RETURNING' . $this->indentCsv($this->returning);    }        public function __construct($host, $port, $user, $password, $db_name, $charset = 'utf8')    {        $this->settings = array(            'host'     => $host,            'port'     => $port,            'user'     => $user,            'password' => $password,            'dbname'   => $db_name,            'charset'  => $charset,        );        $this->connect();    }        protected function connect()    {        $dsn       = 'mysql:dbname=' . $this->settings["dbname"] . ';host=' .            $this->settings["host"] . ';port=' . $this->settings['port'];        $this->pdo = new PDO($dsn, $this->settings["user"], $this->settings["password"],            array(                PDO::MYSQL_ATTR_INIT_COMMAND => 'SET NAMES ' . (!empty($this->settings['charset']) ?                        $this->settings['charset'] : 'utf8')            ));        $this->pdo->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);        $this->pdo->setAttribute(PDO::ATTR_STRINGIFY_FETCHES, false);        $this->pdo->setAttribute(PDO::ATTR_EMULATE_PREPARES, false);    }        public function closeConnection()    {        $this->pdo = null;    }        protected function execute($query, $parameters = "")    {        try {            if (is_null($this->pdo)) {                $this->connect();            }            $this->sQuery = @$this->pdo->prepare($query);            $this->bindMore($parameters);            if (!empty($this->parameters)) {                foreach ($this->parameters as $param) {                    $this->sQuery->bindParam($param[0], $param[1]);                }            }            $this->success = $this->sQuery->execute();        } catch (PDOException $e) {            // 服务端断开时重连一次            if ($e->errorInfo[1] == 2006 || $e->errorInfo[1] == 2013) {                $this->closeConnection();                $this->connect();                try {                    $this->sQuery = $this->pdo->prepare($query);                    $this->bindMore($parameters);                    if (!empty($this->parameters)) {                        foreach ($this->parameters as $param) {                            $this->sQuery->bindParam($param[0], $param[1]);                        }                    }                    $this->success = $this->sQuery->execute();                } catch (PDOException $ex) {                    $this->rollBackTrans();                    throw $ex;                }            } else {                $this->rollBackTrans();                $msg = $e->getMessage();                $err_msg = "SQL:".$this->lastSQL()." ".$msg;                $exception = new \PDOException($err_msg, (int)$e->getCode());                throw $exception;            }        }        $this->parameters = array();    }        public function bind($para, $value)    {        if (is_string($para)) {            $this->parameters[sizeof($this->parameters)] = array(":" . $para, $value);        } else {            $this->parameters[sizeof($this->parameters)] = array($para, $value);        }    }        public function bindMore($parray)    {        if (empty($this->parameters) && is_array($parray)) {            $columns = array_keys($parray);            foreach ($columns as $i => &$column) {                $this->bind($column, $parray[$column]);            }        }    }        public function query($query = '', $params = null, $fetchmode = PDO::FETCH_ASSOC)    {        $query = trim($query);        if (empty($query)) {            $query = $this->build();            if (!$params) {                $params = $this->getBindValues();            }        }        $this->resetAll();        $this->lastSql = $query;        $this->execute($query, $params);        $rawStatement = explode(" ", $query);        $statement = strtolower(trim($rawStatement[0]));        if ($statement === 'select' || $statement === 'show') {            return $this->sQuery->fetchAll($fetchmode);        } elseif ($statement === 'update' || $statement === 'delete' || $statement === 'replace') {            return $this->sQuery->rowCount();        } elseif ($statement === 'insert') {            if ($this->sQuery->rowCount() > 0) {                return $this->lastInsertId();            }        } else {            return null;        }        return null;    }        public function column($query = '', $params = null)    {        $query = trim($query);        if (empty($query)) {            $query = $this->build();            if (!$params) {                $params = $this->getBindValues();            }        }        $this->resetAll();        $this->lastSql = $query;        $this->execute($query, $params);        $columns = $this->sQuery->fetchAll(PDO::FETCH_NUM);        $column  = null;        foreach ($columns as $cells) {            $column[] = $cells[0];        }        return $column;    }        public function row($query = '', $params = null, $fetchmode = PDO::FETCH_ASSOC)    {        $query = trim($query);        if (empty($query)) {            $query = $this->build();            if (!$params) {                $params = $this->getBindValues();            }        }        $this->resetAll();        $this->lastSql = $query;        $this->execute($query, $params);        return $this->sQuery->fetch($fetchmode);    }        public function single($query = '', $params = null)    {        $query = trim($query);        if (empty($query)) {            $query = $this->build();            if (!$params) {                $params = $this->getBindValues();            }        }        $this->resetAll();        $this->lastSql = $query;        $this->execute($query, $params);        return $this->sQuery->fetchColumn();    }        public function lastInsertId()    {        return $this->pdo->lastInsertId();    }        public function lastSQL()    {        return $this->lastSql;    }        public function beginTrans()    {        try {            if (is_null($this->pdo)) {                $this->connect();            }            return $this->pdo->beginTransaction();        } catch (PDOException $e) {            // 服务端断开时重连一次            if ($e->errorInfo[1] == 2006 || $e->errorInfo[1] == 2013) {                $this->closeConnection();                $this->connect();                return $this->pdo->beginTransaction();            } else {                throw $e;            }        }    }        public function commitTrans()    {        return $this->pdo->commit();    }        public function rollBackTrans()    {        if ($this->pdo->inTransaction()) {            return $this->pdo->rollBack();        }        return true;    }}

链式操作的关键是在做完操作后要return $this。return $this表示方法结束后，返回的是当前对象，它可以实现链式操作。

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