12 2019 档案
摘要：select name ,greatest(num1,num2,num3,num4) as max_num -- 最大值 ,least(num1,num2,num3,num4) as min_num -- 最小值 from ( select 'a' as name,1 as num1, 3 as num2, 2 as num3,4 as num4 ) t1 ;
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摘要：列转行 SELECT flag ,substring_index(substring_index(t.context,',', b.help_topic_id + 1), ',', -1) as result FROM ( select 'aa' as flag,'1,2,3,4,5,6,7' as
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