Is there any way to get the if statement to evaluate a query? SELECT if(5>0,'EQ_Type','*') FROM EQUIPMENT; Resulting in: +-----------------------+ | IF(5>0,'EQ_Type','*') | +-----------------------+ | EQ_Type | | EQ_Type | | EQ_Type | | EQ_Type | | EQ_Type | | EQ_Type | | EQ_Type | | EQ_Type | | EQ_Type | +-----------------------+ 9 rows in set (0.00 sec) I would like the above statement to be equivalent to the following: SELECT 'EQ_Type' FROM EQUIPMENT; And produce: +--------------+ | EQ_Type | +--------------+ | ENGINE | | ENGINE | | ENGINE | | TRAILER | | TRAILER | | TRAILER | | WATER TENDER | | WATER TENDER | | WATER TENDER | +--------------+ Thanks for any help
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回答
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只删除单引号。在这种情况下CASE statements - -
SELECT if(5>0,EQ_Type,'*') FROM EQUIPMENT;
+0
谢谢先生。我是新手,所以我认为这将是明显的。 – 2009-12-14 01:23:22
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我建议使用ANSI符号,而不是MySQL的特定语法:
SELECT CASE WHEN 5 > 0 THEN t.eq_type ELSE '*' END
FROM EQUIPMENT t
原因是,如果你改变了数据库 - 这种说法不会需要改变工作在Oracle,Postgres,SQL Server等上。
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Wont 5> 0总是导致'true',因此EQ_Type?我不太了解MySql,所以我可能会误解它。这只是一个人为的例子吗? – GrayWizardx 2009-12-14 01:35:07