对于INSERT、UPDATE、REPLACE、LOAD DATA 以及 LOAD XML 语句,如果违反检查约束将会返回错误。此时,对于已经修改的数据处理取决于存储引擎是否支持事务,以及是否使用了严格 SQL 模式。 对于INSERT IGNORE、UPDATE IGNORE、REPLACE、LOAD DATA … IGNORE 以及 LOAD XML … IGNORE 语句,如果违反检查约束将会返回警告并且跳过...
可以通过以下两种方式定位执行效率较低的 SQL 语句。通过慢查询日志定位那些执行效率较低的 SQL 语句,用--log-slow-queries[=file_name]选项启动时,mysqld 写一个包含所有执行时间超过 long_query_time 秒的 SQL 语句的日志文件。具体可以查看本书第 26 章中日志管理的相关部分。 慢查询日志在查询结束以后才纪录...
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MySQL> alter table t1 add i int; Query OK, 0 rows affected (0.41 sec) Records: 0 Duplicates: 0 Warnings: 0 #然后再次执行sp,就会发现这次执行了这句SQL的prepare再进行execute。 MySQL> call p1; Query OK, 0 rows affected (34.24 sec)
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On is happily pulling the hand which wants to pull, passes through together makes noise lively, waits for together lonely lonely; On is accompanying the human who wants to accompany, happy when smiles together, sad when cries together; Has the heart which wants to have, duplicates the bored ...
in set (0.00 sec) mysql> create table B (id int, name varchar(20)); Query OK, 0 rows affected (0.02 sec) -- A与B表数据类型顺序对应,不需调整 mysql> insert into B select * from A; Query OK, 5 rows affected (0.01 sec) Records: 5 Duplicates: 0 Warnings: 0 mysql> select * ...
...Records: 0 Duplicates: 0 Warnings: 0 UNIQUE约束 UNIQUE约束又称唯一性约束,是指数据表中一列或一组列中只包含唯一值。...MySQL 8.0开始支持CHECK约束。 CONSTRAINT 约束名 CHECK ( 表达式 ) 修改goods表,为商品价格添加CHECK约束,要求价格必须大于0等于。
The first option is to use theUNIQUEconstraint when defining a column in a table. This constraint guarantees that the information in the column is distinct and precludes the addition of any duplicates. To add theUNIQUEconstraint to a column, you need to modify theCREATE TABLEstatement. ...
Records: 2 Duplicates: 0 Warnings: 0 master> SHOW BINLOG EVENTS FROM 261; +---+---+---+---+---+---+ | Log_name | Pos | Event_type | Server_id | End_log_pos | Info | +---+---+---+---+---