Question

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with detail as(
select id,end_time,status from t_wl_record_repairs_detail where end_time is null
)
select COUNT(1) as sum, 'today' as name from detail where end_time is not null and end_time >= '2021-02-04 00:00:00' and `status` > 2
UNION
select COUNT(1) , 'd1' as name from detail where end_time is not null and end_time < '2021-02-04 00:00:00' and `status` < 3
UNION
select COUNT(1), 'd7' as name from detail where end_time is not null and end_time < '2021-01-29 00:00:00' and `status` < 3
UNION
select COUNT(1), 'd30' as name from detail where end_time is not null and end_time < '2021-01-06 00:00:00' and `status` < 3;

我想这样写sql，但是不行。mysql 5.6支持[with..as()]语法吗？

Answer 1

不，Common Table Expressions（WITH 子句的名称）是在 MySQL 8 中引入的。它们不能在 5.6 中使用。相反，我们通常会加入旧 MySQL 版本中的子查询。

对于像您这样的查询，您在多个 UNION 组件中重用相同的公共表表达式，而不是子查询，我建议将其选择到一个临时表中，然后在您的 UNION查询。

CREATE TEMPORARY TABLE detail 
  SELECT id, end_time, status
  FROM t_wl_record_repairs_detail
  WHERE end_time IS NULL;

SELECT COUNT(1) as sum, 'today' as name FROM detail...
UNION
SELECT COUNT(1) as sum, 'd1' as name....
UNION...

更新：

MySQL has documented 表明不能多次引用临时表，例如在 UNION 中。

使用巧妙的 CASE 链并且没有临时表或 CTE，这仍然是可行的。

SELECT
  COUNT(1) AS sum,
  CASE 
    WHEN end_time end_time >= '2021-02-04 00:00:00' and `status` > 2 THEN 'today'
    WHEN end_time < '2021-02-04 00:00:00' and `status` < 3 THEN 'd1'
    WHEN end_time < '2021-01-29 00:00:00' and `status` < 3 THEN 'd7'
    WHEN end_time < '2021-01-06 00:00:00' and `status` < 3 THEN 'd30'
    ELSE 'other'
  END AS name
FROM t_wl_record_repairs_detail
GROUP BY name

mysql 5.6 是否支持 [ with.. as() ] 语法？

1 个答案:

更新：