這跟前一篇 自動補足列數
所以必須計算UNION後的資料列數,語法如下
SELECT SUM(num) as num FROM( SELECT COUNT(*) as num FROM tbl1 WHERE condition1='cond1' UNION SELECT COUNT(*) as num FROM tbl2 WHERE condition2='cond2' UNION SELECT COUNT(*) as num FROM tbl3 WHERE condition3='cond3' ) as rows) |
就是把條件下的總列數UNION後再一次SUM起來就可以得到答案了
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