select namea as name,agea as age from tablea
union all
select nameb as name,ageb as age from tableb
union all
select namec as name,agec as age from tablec
union all
select named as name,aged as age from tabled这条sql语句查询时非常的慢 如果在存储过程里面改写 怎么弄呢
各位高手帮忙看看吧 谢谢!
union all
select nameb as name,ageb as age from tableb
union all
select namec as name,agec as age from tablec
union all
select named as name,aged as age from tabled这条sql语句查询时非常的慢 如果在存储过程里面改写 怎么弄呢
各位高手帮忙看看吧 谢谢!
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如果想对合并后的结果查询,那就在几个表上需要查询的字段建好索引,然后上层建视图CREATE OR REPLACE VIEW V AS
SELECT ... FROM A1
UNION ALL
SELECT ... FROM A2
...
/
sql没法子优化,都得这么写