如果有的话，比a和b都取出来再做判断来说效率如何？
This topic created in 4367 days ago, the information mentioned may be changed or developed.
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abelyaoNov 20, 2014
1
不是应该用字段默认值吗
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abelyaoNov 20, 2014
4
SELECT IFNULL(A, B) 试试看…
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yanleijavaNov 20, 2014
5
case when 啊
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zts1993Nov 20, 2014
6
case when 大法好
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fengchangNov 20, 2014
7
case when a='' then b else a end
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ozkingNov 20, 2014
8
COALESCE
http://dev.mysql.com/doc/refman/5.0/en/comparison-operators.html#function_coalesce 效率肯定比你自己取出来再比较高 |
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hiswayNov 20, 2014
9
COALESCE(A,B) 今天刚用到～
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incompatibleNov 20, 2014
10
case when写出来太冗长了
ifnull和coalesce就够用了 |
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