首先mysql更新數(shù)據(jù)的某個字段，一般這樣寫：
UPDATE mytable SET myfield = 'value' WHERE other_field = 'other_value';
也可以這樣用in指定要更新的記錄：
UPDATE mytable SET myfield = 'value' WHERE other_field in ('other_values');這里注意 ‘other_values' 是一個逗號（，）分隔的字符串，如：1,2,3
如果更新多條數(shù)據(jù)而且每條記錄要更新的值不同，可能很多人會這樣寫：
foreach ($values as $id => $myvalue) { $sql = "UPDATE mytable SET myfield = $myvalue WHERE id = $id"; mysql_query($sql);}即是循環(huán)一條一條的更新記錄。一條記錄update一次，這樣性能很差，也很容易造成阻塞。
那么能不能一條sql語句實現(xiàn)批量更新呢？
mysql并沒有提供直接的方法來實現(xiàn)批量更新，但是可以用點小技巧來實現(xiàn)。
UPDATE mytable SET myfield = CASE id WHEN 1 THEN 'myvalue1' WHEN 2 THEN 'myvalue2' WHEN 3 THEN 'myvalue3' ENDWHERE other_field ('other_values')如果where條件查詢出記錄的id不在CASE范圍內(nèi)，myfield將被設置為空。
如果更新多個值的話，只需要稍加修改：
UPDATE mytable SET myfield1 = CASE id WHEN 1 THEN 'myvalue11' WHEN 2 THEN 'myvalue12' WHEN 3 THEN 'myvalue13' END, myfield2 = CASE id WHEN 1 THEN 'myvalue21' WHEN 2 THEN 'myvalue22' WHEN 3 THEN 'myvalue23' ENDWHERE id IN (1,2,3)
這里以php為例，構(gòu)造這兩條mysql語句：
1、更新多條單個字段為不同值, mysql模式
$ids_values = array( 1 => 11, 2 => 22, 3 => 33, 4 => 44, 5 => 55, 6 => 66, 7 => 77, 8 => 88,); $ids = implode(',', array_keys($ids_values ));$sql = "UPDATE mytable SET myfield = CASE id ";foreach ($ids_values as $id=> $myvalue) { $sql .= sprintf("WHEN %d THEN %d ", $id, $myvalue);}$sql .= "END WHERE id IN ($ids)";echo $sql.";<br/>";輸出：
UPDATE mytable SET myfield = CASE id WHEN 1 THEN 11 WHEN 2 THEN 22 WHEN 3 THEN 33 WHEN 4 THEN 44 WHEN 5 THEN 55 WHEN 6 THEN 66 WHEN 7 THEN 77 WHEN 8 THEN 88 END WHERE id IN (1,2,3,4,5,6,7,8);
2、更新多個字段為不同值, PDO模式
$data = array(array('id' => 1, 'myfield1val' => 11, 'myfield2val' => 111), array('id' => 2, 'myfield1val' => 22, 'myfield2val' => 222));$where_in_ids = implode(',', array_map(function($v) {return ":id_" . $v['id'];}, $data));$update_sql = 'UPDATE mytable SET';$params = array();$update_sql .= ' myfield1 = CASE id';foreach($data as $key => $item) { $update_sql .= " WHEN :id_" . $key . " THEN :myfield1val_" . $key . " "; $params[":id_" . $key] = $item['id']; $params[":myfield1val_" . $key] = $item['myfield1val'];}$update_sql .= " END";$update_sql .= ',myfield2 = CASE id';foreach($data as $key => $item) { $update_sql .= " WHEN :id_" . $key . " THEN :myfield2val_" . $key . " "; $params[":id_" . $key] = $item['id']; $params[":myfield1va2_" . $key] = $item['myfield2val'];}$update_sql .= " END";$update_sql .= " WHERE id IN (" . $where_in_ids . ")";echo $update_sql.";<br/>";var_dump($params);輸出：
UPDATE mytable SET myfield1 = CASE id WHEN :id_0 THEN :myfield1val_0 WHEN :id_1 THEN :myfield1val_1 END,myfield2 = CASE id WHEN :id_0 THEN :myfield2val_0 WHEN :id_1 THEN :myfield2val_1 END WHERE id IN (:id_1,:id_2);array (size=6) ':id_0' => int 1 ':myfield1val_0' => int 11 ':id_1' => int 2 ':myfield1val_1' => int 22 ':myfield1va2_0' => int 111 ':myfield1va2_1' => int 222
另外三種批量更新方式
1. replace into 批量更新
replace into mytable(id, myfield) values (1,'value1'),(2,'value2'),(3,'value3');
2. insert into ...on duplicate key update批量更新
insert into mytable(id, myfield1, myfield2) values (1,'value11','value21'),(2,'value12','value22'),(3,'value13','value23') on duplicate key update myfield1=values(myfield2),values(myfield2)+values(id);
3. 臨時表
DROP TABLE IF EXISTS `tmptable`;create temporary table tmptable(id int(4) primary key,myfield varchar(50));insert into tmptable values (1,'value1'),(2,'value2'),(3,'value3');update mytable, tmptable set mytable.myfield = tmptable.myfield where mytable.id = tmptable.id;
總結(jié)
以上就是這篇文章的全部內(nèi)容了，希望本文的內(nèi)容對大家的學習或者工作能帶來一定的幫助，如果有疑問大家可以留言交流。
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