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. ...
测试性能:使用如下代码进行性能测试。 SETprofiling=1;DELETEFROMtable_nameWHEREidIN(1,2,3);SHOWPROFILES;SHOWPROFILEALLFORQUERY1; 1. 2. 3. 4. 执行删除操作: DELETEFROMtable_nameWHEREidIN(1,2,3); 1. 四、状态图 下面是解决"mysql delete in 性能问题"的状态图: 完成分析选择分批删除方式选择其他方...
DELETE 语句: mysql> use RUNOOB; Database changed mysql> DELETE FROM runoob_tbl WHERE runoob_id=3; Query OK, 1 row affected (0.23 sec)使用PHP 脚本删除数据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。
I need to delete a row in mysql database. The condition values in the where clause is a varchar and contains hyphens. my query looks like: "DELETE from TestTable Where TestID = " + testid + ";"; The testid value containd hyphen (for ex: dis-connect) ...
for_delete; Query OK, 3 rows affected (0.04 sec) mysql> insert for_delete (name) values ('D'); Query OK, 1 row affected (0.02 sec) mysql> select * from for_delete; +---+---+ | id | name | +---+---+ | 4 | D | +---+---+ 1 row in set (0.00 sec)截断表 trunca...
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 = ...
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。
delete from tu where id in (3,4); Query OK, 2 rows affected (0.00 sec) ---TRANSACTION 146880, ACTIVE 1 sec 2 lock struct(s), heap size 360, 2 row lock(s), undo log entries 2 MySQL thread id 1, OS thread handle 0x7f61ab1c7700, query id 928 localhost msandbox cleaning up ...
mysql>deletefromstudents2; Query OK,2rowsaffected (0.04sec) mysql>select*fromstudents2;Emptyset(0.00sec) (2)多表 被删除的表不能出现在查询子句的子查询中; Low_priority表示删除语句需要等待其他链接的读此表操作结束后再执行,只作用于MyISAM,MEMORY和MERGE存储引擎 ...
mysql>create user'testuser01'@'%'identified by'Test01.~!#';QueryOK,0rowsaffected(0.01sec) 通过上面的例子发现,第一次创建用户testuser01之后,使用的drop的方式将用户删除,我们重新创建用户,正常创建用户成功,这时候大家会想这有啥问题吗?接着往下看, ...