如何优化SQL Server查询

Question

我正在将数据从一个表复制到另一个表。在复制时我正在做一些计算来修改一列。

SQL Server查询：

INSERT INTO rat_proj_duration_map_2 
    SELECT 
    r.*, 
    r.hour_val/(CASE 
     WHEN week_val = 1 AND 
     (SELECT TOP 1 
      hrswk 
     FROM UserProfileRATinterface_view us 
     INNER JOIN users u 
      ON u.username = us.username 
     WHERE calwk = 2 
     AND r.uid = u.uid 
     AND yr = 2016) 
     > 0 THEN (SELECT TOP 1 
      hrswk 
     FROM UserProfileRATinterface_view us 
     INNER JOIN users u 
      ON u.username = us.username 
     WHERE calwk = 2 
     AND r.uid = u.uid 
     AND yr = 2016) 
     WHEN (SELECT 
      hrswk 
     FROM UserProfileRATinterface_view us 
     INNER JOIN users u 
      ON u.username = us.username 
     WHERE r.week_val = us.calwk 
     AND r.uid = u.uid 
     AND yr = 2016) 
     < 1 AND 
     (SELECT 
      MAX(hrswk) 
     FROM UserProfileRATinterface_view us 
     INNER JOIN users u 
      ON u.username = us.username 
     WHERE r.uid = u.uid 
     AND yr = 2016) 
     > 0 THEN (SELECT 
      MAX(hrswk) 
     FROM UserProfileRATinterface_view us 
     INNER JOIN users u 
      ON u.username = us.username 
     WHERE r.uid = u.uid 
     AND yr = 2016) 
     WHEN (SELECT 
      COUNT(*) 
     FROM UserProfileRATinterface_view us 
     INNER JOIN users u 
      ON u.username = us.username 
     WHERE r.uid = u.uid 
     AND yr = 2016) 
     <= 0 THEN 1 
     ELSE (SELECT 
      hrswk 
     FROM UserProfileRATinterface_view us 
     INNER JOIN users u 
      ON u.username = us.username 
     WHERE r.week_val = us.calwk 
     AND r.uid = u.uid 
     AND yr = 2016) 
    END) * 100 AS percentage_val 
    FROM rat_proj_duration_map r 

当我运行此查询我得到超时问题。

提供的TCP：超时错误[258]

SQL Server是不是在我的手，增加超时值。

是否可以优化我的SQL查询？

Answer 1

您的case子句中的子查询看起来基本相同。您可以通过定义此子查询的分组版本（... where yr=2016 group by u.uid）（最好将其作为公用表表达式）来简化整个命令，然后使用该命令。这可能会节省大量冗余操作。

下可能工作（没有测试过）：

;WITH usrall as (
SELECT u.uid ui, hrswk hw, r.week wk, us.calwk cw 
FROM UserProfileRATinterface_view us 
INNER JOIN users u on u.username=us.username 
WHERE r.uid=u.uid and yr=2016 
), usrgrp as (
SELECT ui gui, MAX(hrswk) ghw, count(*) gcnt FROM usrall group by ui 
), denom as (
SELECT gui dui, COALESCE(MAX(w2.hw), MAX(wkwc.hw), MAX(gwh)) dnm 
FROM usrgrp 
LEFT JOIN usrall w2 ON w2.ui=gui AND w2.cw=2 AND w2.hw>0 
LEFT JOIN usrall wkcw ON wkcw.ui=gui AND wkcw.wk=wkcw.cw AND wkwc.hw<1 
GROUP BY gui 
)   
SELECT r.*, r.hour_val/d.dnm 
FROM rat_proj_duration_map r 
INNER JOIN denom d ON d.dui=u.uid 

基本上我已经试过（我希望它的工作原理： - /）取代的情况下由COALESCE()功能检查三种可能计算的构建一个接一个地值。第一个非空值被接受。

正如我所说：我没有测试过它。祝你好运

Answer 2

你确定这个查询在逻辑上是正确的吗？你有几个TOP 1 s没有具体ORDER BY，子标记比较没有TOP子选择（我假设，如果您在其他子查询中使用top具有相同的来源，可能会返回多个行）。

是的 - 这个查询可以优化。你可以得到你需要一个子查询语句中的所有值，避免同一子查询的多个执行的rat_proj_duration_map的每一行，你现在有：

INSERT INTO rat_proj_duration_map_2 
    SELECT 
     r.*, 
     r.hour_val/(CASE 
           WHEN week_val = 1 AND us.min_hrswk_2 > 0 
           THEN us.min_hrswk_2 
           WHEN us.min_hrswk_week_val <1 
           AND max_hrswk > 0 
           THEN max_hrswk 
           WHEN us.cnt <= 0 
           THEN 1 
           ELSE min_hrswk_week_val 
          END) * 100 as percentage_val 
    FROM 
     rat_proj_duration_map r 
    OUTER APPLY 
    (
     SELECT 
      count(*) as cnt, 
      MIN(CASE WHEN calcw = 2 THEN hrswk END) as min_hrswk_2, 
      MIN(CASE WHEN calcw = r.week_val THEN hrswk END) as min_hrswk_week_val, 
      MAX(hrswk) as max_hrswk 
     FROM UserProfileRATinterface_view us 
     inner join users u on u.username=us.username 
     WHERE r.uid=u.uid and yr=2016 
    ) us 

但我不能肯定，如果原来的逻辑是正确的。而这种情况下，我的想法是这样的：

... 
    r.hour_val/COALESCE(NULLIF(us.min_hrswk_2, 0), 
     NULLIF(us.min_hrswk_week_val, 0), NULLIF(max_hrswk, 0), 1) 
...