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在计数内选择

mysql sql

Clayton · 技术社区 · 15 年前

我想在计数中嵌入SELECT,但找不到任何示例。

#pseudosql
SELECT a AS current_a, COUNT(*) AS b,
   COUNT( SELECT FROM t WHERE a = current_a AND c = 'const' ) as d,
   from t group by a order by b desc

4 回复 | 直到 15 年前

Justin K 15 年前

SELECT a, COUNT(*) AS b,
   SUM( CASE WHEN c = 'const' THEN 1 ELSE 0 END ) as d,
   from t group by a order by b desc

Ike Walker 15 年前

您可以将count()移动到子选择中:

SELECT a AS current_a, COUNT(*) AS b,
   ( SELECT COUNT(*) FROM t WHERE a = current_a AND c = 'const' ) as d,
   from t group by a order by b desc

Femaref 15 年前

使用 SELECT COUNT(*) FROM t WHERE a = current_a AND c = 'const' ) as d .

-1

Jeroen 15 年前

SELECT a AS current_a, COUNT(*) AS b,
   (SELECT COUNT(*) FROM t WHERE a = current_a AND c = 'const' ) as d
   from t group by a order by b desc

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