mysql> select t1.a from t1 join t2 on t1.a = t2.a; +---+ | a | +---+ | 4 | +---+ 1 row in set (0.00 sec) mysql> select t1.a from t1 join t2 on t1.a = t2.a; +---+ | a | +---+ | 4 | +---+ 1 row in set (0.00 sec) 1. 2. 3. 4. 5. 6. ...
insert into aa values(3, 'c', 3); explain select b from aa where b in ('a','ab'); 可以得到如下的查询执行计划: test=# explain select b from aa where b in ('a','ab'); QUERY PLAN --- Bitmap Heap Scan on aa (cost=8.52..13.86 rows=2 width=38) Recheck Cond: ((b)::tex...
因此,就需要DBA来不断的优化SQL。 对于查询情况,其实MySQL提供给我们一个功能来引导优化器更好的优化,那便是MySQL的查询优化提示(Query Optimizer Hints)。比如,想让SQL强制走索引的话,可以使用 FORCE INDEX 或者USE INDEX;它们基本相同,不同点:在于就算索引的实际用处不大,FORCE INDEX也得要使用索引。 EXPLAIN SEL...
$result=getSQL($query); if($result==1){ $result = getSQL("commit"); } return $result; } getSQL() is a just a simple function i use to create the db connection and run the query, no logic there. --- I also tried printing the delete query generated and ran the same manually ...
mysql> update studentsetage=18wherename='邱导'; Query OK,2rows affected (0.01sec) Rows matched:2Changed:2Warnings:0mysql>select* from student; +---+---+---+---+---+---+ | id | name | age | gender | cometime | birthday | +---+---+---+---+---+---+ |1| 邱导 ...
PHP使用 mysqli_query() 函数来执行SQL语句, 你可以在 SQL DELETE 命令中使用或不使用 WHERE 子句。该函数与 mysql> 命令符执行SQL命令的效果是一样的。 MySQL DELETE 语句测试以下PHP实例将删除 runoon_tbl 表中 runoon_id 为 3 的记录: <?php$dbhost = ...
PHP 使用 mysqli_query() 函数来执行SQL语句, 你可以在 DELETE 命令中使用或不使用 WHERE 子句。 该函数与mysql>命令符执行SQL命令的效果是一样的。 实例 以下PHP实例将删除 runoob_tbl 表中 runoob_id 为 3 的记录: MySQL DELETE 子句测试: <?php$dbhost='localhost';//mysql服务器主机地址$dbuser='root...
Query OK,1row affected (0.03sec) mysql>select*fromstudents2;+---+---+---+---+ | sid | sname | gender | dept_id | +---+---+---+---+ |100| zhangsan | male |1| |101| zhangsan | male |10| +---+---+---+---+2rows...
mysql tables in use 1, locked 1 LOCK WAIT 18 lock struct(s), heap size 1136, 58 row lock(s), undo log entries 41 MySQL thread id 298, OS thread handle 140425685493504, query id 5479767 172.18.70.114 root updating delete from session where id in (x'B41D1ACB485A4E599A687E4AB1C36648...
DELETE query in PHPPosted by: Ugis Revelis Date: July 28, 2005 06:20AM Hi! I spent 3 h to figure out how to write this query and still nothing... The problem is, that I have 3 tables and if I delete some record from the first table, I want to delete from other 2 ...