计算input_expression,然后按指定顺序对每个 WHEN 子句的 input_expression = when_expression 进行计算。 返回第一个取值为 TRUE 的 (input_expression = when_expression) 的 result_expression。 如果没有取值为 TRUE 的 input_expression = when_expr
The trigger can be executed when you run one of the following MySQL statements on the table: INSERT, UPDATE and DELETE and it can be invoked before or
You may find theMySQL User Forumshelpful when working with triggers. For answers to commonly asked questions regarding triggers in MySQL, seeSection A.5, “MySQL 8.4 FAQ: Triggers”. There are some restrictions on the use of triggers; seeSection 27.8, “Restrictions on Stored Programs”. ...
CREATETRIGGERtrigger_ name # the trigger name{BEFORE|AFTER}# when the trigger activates{INSERT|UPDATE|DELETE}# what statement activates itONtbl_ name # the associated tableFOREACHROWtrigger_ stmt;# what the trigger does 来个栗子看看: 代码语言:javascript 代码运行次数:0 运行 AI代码解释 CREATETABLE...
192.168.2.128 [root ~]$ mysqldump -uroot -p123456 --master-data=2 --single-transaction -R --triggers -A > all.sql 其中--master-data=2代表备份时刻记录master的Binlog位置和Position,--single-transaction意思是获取一致性快照,-R意思是备份存储过程和函数,--triggres的意思是备份触发器,-A代表备份所...
create trigger trigger_name {before | after} {insert | update | delete} on tabl_name for each row trigger_stmt 上述语法说明: (1)trigger_name:触发器名称。 (2)before | after:触发程序的动作时间,在触发事件之前还是之后触发语句。 (3)insert | update | delete:触发条件。
you can also change its value withSET NEW.col_name=valueif you have theUPDATEprivilege for it. This means you can use a trigger to modify the values to be inserted into a new row or used to update a row. (Such aSETstatement has no effect in anAFTERtrigger because the row change wil...
Triggers are often used to maintain the integrity of data across tables of an application. When a user on a website makes a purchase, for example, the first action that occurs in the database may be that a credit is inserted into an accounting table. ...
Temporary tables.CREATE TEMPORARY TABLEandDROP TEMPORARY TABLEstatements are not supported inside transactions, procedures, functions, and triggers when using GTIDs (that is, when theenforce_gtid_consistencysystem variable is set toON). It is possible to use these statements with GTIDs enabled, but...
use 是建议,实际使用哪个索引 MySQL 还会自己权衡运行速度去更改,force就是无论如何都强制使用该索引。 覆盖索引&回表查询 尽量使用覆盖索引(查询使用了索引,并且需要返回的列,在该索引中已经全部能找到),减少 select *。 explain 中 extra 字段含义: using index condition:查找使用了索引,但是需要回表查询数据 using...