sql查询问题

Question

给定一个起始日期，查询特定内容，没有的内容补充为0

Answer 1

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SELECT DATE_FORMAT(DATE_SUB(NOW(), INTERVAL xc MONTH), '%Y-%m') as date
FROM (
         SELECT @xi:=@xi+1 as xc from
                                     (SELECT 1 UNION SELECT 2 UNION SELECT 3 UNION SELECT 4 UNION SELECT 5) xc1,
                                     (SELECT 1 UNION SELECT 2 UNION SELECT 3 UNION SELECT 4 UNION SELECT 5) xc2,
                                     (SELECT @xi:=0) xc0
     ) xcxc

Answer 2

执行sql后,如果没有内容直接用程序判断补充为0不就行了

Answer 3

如果查询的内容是指定长度的可以使用rpad或者lpad函数试试，RPAD(str, len, padstr)