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MySQL中怎么創(chuàng)建一個(gè)觸發(fā)器,很多新手對(duì)此不是很清楚,為了幫助大家解決這個(gè)難題,下面小編將為大家詳細(xì)講解,有這方面需求的人可以來學(xué)習(xí)下,希望你能有所收獲。
--創(chuàng)建測(cè)試表
MariaDB [test]> create table account (acct_num int, amount decimal(10,2));
Query OK, 0 rows affected (0.16 sec)
--創(chuàng)建觸發(fā)器
MariaDB [test]> CREATE TRIGGER ins_sum BEFORE INSERT ON account
-> FOR EACH ROW SET @sum = @sum + NEW.amount;
Query OK, 0 rows affected (0.08 sec)
MariaDB [test]> select @sum;
+------+
| @sum |
+------+
| NULL |
+------+
1 row in set (0.00 sec)
MariaDB [test]> SET @sum = 0;
Query OK, 0 rows affected (0.00 sec)
MariaDB [test]> INSERT INTO account VALUES(137,14.98),(141,1937.50),(97,-100.00);
Query OK, 3 rows affected (0.08 sec)
Records: 3 Duplicates: 0 Warnings: 0
MariaDB [test]> select @sum;
+---------+
| @sum |
+---------+
| 1852.48 |
+---------+
1 row in set (0.00 sec)
MariaDB [test]> select sum(amount) from account;
+-------------+
| sum(amount) |
+-------------+
| 1852.48 |
+-------------+
1 row in set (0.00 sec)
--查看觸發(fā)器
MariaDB [test]> show triggers\G
*************************** 1. row ***************************
Trigger: ins_sum
Event: INSERT
Table: account
Statement: SET @sum = @sum + NEW.amount
Timing: BEFORE
Created: NULL
sql_mode: NO_AUTO_CREATE_USER,NO_ENGINE_SUBSTITUTION
Definer: root@localhost
character_set_client: utf8
collation_connection: utf8_general_ci
Database Collation: utf8_general_ci
1 row in set (0.00 sec)
MariaDB [test]> select * from information_schema.triggers where trigger_name='ins_sum' \G
*************************** 1. row ***************************
TRIGGER_CATALOG: def
TRIGGER_SCHEMA: test
TRIGGER_NAME: ins_sum
EVENT_MANIPULATION: INSERT
EVENT_OBJECT_CATALOG: def
EVENT_OBJECT_SCHEMA: test
EVENT_OBJECT_TABLE: account
ACTION_ORDER: 0
ACTION_CONDITION: NULL
ACTION_STATEMENT: SET @sum = @sum + NEW.amount
ACTION_ORIENTATION: ROW
ACTION_TIMING: BEFORE
ACTION_REFERENCE_OLD_TABLE: NULL
ACTION_REFERENCE_NEW_TABLE: NULL
ACTION_REFERENCE_OLD_ROW: OLD
ACTION_REFERENCE_NEW_ROW: NEW
CREATED: NULL
SQL_MODE: NO_AUTO_CREATE_USER,NO_ENGINE_SUBSTITUTION
DEFINER: root@localhost
CHARACTER_SET_CLIENT: utf8
COLLATION_CONNECTION: utf8_general_ci
DATABASE_COLLATION: utf8_general_ci
1 row in set (0.00 sec)
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