mysql case的语法
2024-09-28 06:38:47
测试表：team
第一种语法：
CASE case_value
WHEN when_value THEN statement_list
[WHEN when_value THEN statement_list] ...
[ELSE statement_list]
END CASE
mysql> select * from team;
+------+
| name |
+------+
| a |
| b |
| c |
| d |
+------+
rows in set (0.00 sec) mysql> select case name when 'a' then 'aaa' when 'b' then 'bbb' when 'c' then 'ccc' when 'd' then 'ddd' end from team;
+------------------------------------------------------------------------------------------------+
| case name when 'a' then 'aaa' when 'b' then 'bbb' when 'c' then 'ccc' when 'd' then 'ddd' end |
+------------------------------------------------------------------------------------------------+
| aaa |
| bbb |
| ccc |
| ddd |
+------------------------------------------------------------------------------------------------+
rows in set (0.00 sec) mysql> select case name when 'a' then 'aaa' when 'b' then 'bbb' when 'c' then 'ccc' when 'd' then 'ddd' else 'eee' end from team;
+-----------------------------------------------------------------------------------------------------------+
| case name when 'a' then 'aaa' when 'b' then 'bbb' when 'c' then 'ccc' when 'd' then 'ddd' else 'eee' end |
+-----------------------------------------------------------------------------------------------------------+
| aaa |
| bbb |
| ccc |
| ddd |
+-----------------------------------------------------------------------------------------------------------+
rows in set (0.00 sec)
第二种语法：
CASE
WHEN search_condition THEN statement_list
[WHEN search_condition THEN statement_list] ...
[ELSE statement_list]
END CASE
mysql> select (case when name='a' then 'aaa' when name='b' then 'bbb' when name='c' then 'ccc' when name='d' then 'ddd' else 'ccc' end) alias from team;
+-------+
| alias |
+-------+
| aaa |
| bbb |
| ccc |
| ddd |
+-------+
rows in set (0.00 sec)
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