调整查询以使用 CTE

Question

我正在寻找在查询中使用 CTE，因为我得到了相同的选择，但我以前从未使用过 CTE，有人可以帮助我吗？

我需要 firstTable 可以在其他选择中使用

SELECT firstTable.id as id,
   secondTable.holder as holder
FROM (
select tb3.id as id
from table1 tb1
inner join table2 tb2 on tb1.tb2_id = tb2.id
inner join table3 tb3 on tb2.tb3_id = tb3.id and tb3.id
inner join table4 tb4 on tb4.id = tb3.tb4_id and tb4.id = 1998
group by tb3.id) as firstTable
JOIN (
select id_holder,
       sum(temporaryTable.holder) as holder
from (
    select cast(tb4.helper as integer) as helper,
           count(distinct tb4.id) as holder,
           tb3.id as id_holder
    from table1 tb1
    inner join table2 tb2 on tb1.tb2_id = tb2.id
    inner join table3 tb3 on tb2.tb3_id = tb3.id and tb3.id
    inner join table4 tb4 on tb4.id = tb3.tb4_id and tb4.id = 1998
    group by tb3.id, tb4.helper
) as temporaryTable
where temporaryTable.helper between 7 and 8
group by id_holder) as secondTable
ON firstTable.id = temporaryTable.id_holder

这是我的尝试查询：

WITH temporary_table AS
  ( SELECT id,
           cast(resp.valor AS integer) AS holder,
           count(val) AS sumId
   FROM table1 tb1
   INNER JOIN table2 tb2 ON tb1.tb2_id = tb2.id
   INNER JOIN table3 tb3 ON tb2.tb3_id = tb3.id
   AND tb3.id
   INNER JOIN table4 tb4 ON tb4.id = tb3.tb4_id
   AND tb4.id = 1998
   GROUP BY tb3.id )
SELECT
  (SELECT SUM(sumId)
   WHERE holder = -10) AS p1,

  (SELECT SUM(sumId)
   WHERE holder = 78) AS p2,

  (SELECT SUM(sumId)
   WHERE holder = 1997) AS p3,
       id
FROM temporary_table
GROUP BY id,
         holder;

Answer 1

试试这个查询：

select tb3.id as id,
       count(distinct CASE WHEN tb4.helper between 7 and 8 THEN tb4.id END) as holder,
from table1 tb1
inner join table2 tb2 on tb1.tb2_id = tb2.id
inner join table3 tb3 on tb2.tb3_id = tb3.id and tb3.id
inner join table4 tb4 on tb4.id = tb3.tb4_id and tb4.id = 1998
group by tb3.id

Answer 2

对每个子查询使用 CTE 非常简单：

WITH firstTable AS (
    select tb3.id as id
    from table1 tb1
        inner join table2 tb2 on tb1.tb2_id = tb2.id
        inner join table3 tb3 on tb2.tb3_id = tb3.id and tb3.id
        inner join table4 tb4 on tb4.id = tb3.tb4_id and tb4.id = 1998
    group by tb3.id
), temporaryTable AS (
    select cast(tb4.helper as integer) as helper,
           count(distinct tb4.id) as holder,
           tb3.id as id_holder
    from table1 tb1
        inner join table2 tb2 on tb1.tb2_id = tb2.id
        inner join table3 tb3 on tb2.tb3_id = tb3.id and tb3.id
        inner join table4 tb4 on tb4.id = tb3.tb4_id and tb4.id = 1998
    group by tb3.id, tb4.helper
), secondTable AS (
select id_holder,
       sum(temporaryTable.holder) as holder
from temporaryTable
where temporaryTable.helper between 7 and 8
group by id_holder
)
    SELECT firstTable.id as id,
       secondTable.holder as holder
    FROM firstTable
        JOIN secondTable
            ON firstTable.id = temporaryTable.id_holder;

Answer 3

我将仅提供问题本身的切线。

我强烈建议您不要使用 CTE。如果您想要一个看起来不错的优雅查询，我相信正确格式化您的查询会更好。 http://www.dpriver.com/pp/sqlformat.htm

CTE 有一个固有的问题是速度很慢，因为在大多数情况下索引都没有正确触发。多年来，我一直从事 SQL 作为职业，在 CTE 中遇到了很多性能问题。使 CTE 更快是困难的，我认为不值得付出努力。它们也使调试和测试查询变得很痛苦，尤其是当 CTE 中有很多表时。很难划分子查询，尤其是测试前一个子查询的假设是否仍然有效。

您还可以在 stackoverflow 中查看以下至少 500 多个关于 CTE 速度慢的问题： https://stackoverflow.com/search?q=slow+cte

我的建议是将数据放在临时表中。您还可以通过重用临时表来删除重复的代码。作为获得更好性能的额外奖励，您可以在临时表中创建索引。您不能在 CTE 中动态创建索引。在我看来，使用 CTE 的唯一原因是递归 CTE。 https://www.essentialsql.com/recursive-ctes-explained/