SQL Server T-SQL查詢優化

Question

我正在嘗試優化以下T-SQL查詢：

SELECT Person.*
FROM Person
WHERE ZipCode LIKE '123%'
AND City = 'Washington'
AND NumberOfHomes in (1, 2, 3)
AND
(
    EXISTS
    (
        SELECT * FROM House
        WHERE Person.ID = House.PersonID
        AND House.Type = 'TOWNHOUSE'
        AND House.Size = 'Medium'
    )
    OR
    EXISTS
    (
        SELECT * FROM Color
        WHERE Person.ID = Color.PersonID
        AND Color.Foreground IN ('Green', 'Blue', 'Purple')
    )
)

我非常感謝優化查詢的任何響應。

特別是，有沒有辦法只使用一個沒有任何內部SELECT語句的SELECT語句將查詢轉換為更有效的查詢？

謝謝！

Answer 1

這是查詢：

SELECT p.* 
FROM Person p
WHERE p.ZipCode LIKE '123%'  AND p.City = 'Washington' AND p.NumberOfHomes in (1, 2, 3) AND
      (EXISTS (SELECT *
               FROM House h
               WHERE p.ID = h.PersonID AND h.Type = 'TOWNHOUSE' AND h.Size = 'Medium'
             ) OR 
       EXISTS (SELECT *
               FROM Color c
               WHERE p.ID = c.PersonID AND c.Foreground IN ('Green', 'Blue', 'Purple')
              )
      );

如果不重寫查詢，可以使用索引對其進行優化。 我建議：

Person(City, ZipCode, NumberOfHomes, Id);
House(PersonId, Type, Size);
Color(PersonID, Foreground)

但問題是。 你確定的ID s in the家and顏色tables really match back to Person.Id ? Normally, they would have a column called something like ? Normally, they would have a column called something like PersonId` ? Normally, they would have a column called something like 。

Answer 2

左連接和檢查null將比進行存在檢查更快。 此外，如果NumberofHomes是一個整數，則BETWEEN將與IN相同。

SELECT p.*
FROM Person p
LEFT JOIN House h
    ON p.ID = h.PersonID
    AND h.Type = 'TOWNHOUSE'
    AND h.Size = 'Medium'
LEFT JOIN Color c
    ON p.ID = c.PersonID
    AND c.Foreground IN ('Green', 'Blue', 'Purple')
WHERE p.ZipCode LIKE '123%'
  AND p.City = 'Washington'
  AND p.NumberOfHomes BETWEEN 1 AND 3
  AND (h.PersonID is not null or c.PersonID is not null)

或者你可以嘗試這樣的東西......

select t.* 
from (
    select personid from house
    where type = 'townhouse' and size = 'medium'
    union
    select personid from color
    where foreground in ('green','blue','purple')
) pid
cross apply (
    select *
    from person p
    where p.id = pid.personid
      and p.zipcode like '123%'
      and p.city = 'washington'
      and p.numberofhomes between 1 and 3
    ) t
where t.id is not null

優化這些盲人真的很難。 根據您的數據分布，上述查詢可能會給您帶來更好的結果。

Answer 3

請試試這個：

SELECT p.*
FROM Person p
WHERE Substring(Ltrim(Rtrim(p.ZipCode)),1,3) = '123' AND p.City = 'Washington'AND 
(p.NumberOfHomes=1 or  p.NumberOfHomes=2 or p.NumberOfHomes=3))
AND
(
EXISTS
(
    SELECT 1 FROM House h
    WHERE p.ID = h.PersonID
    AND h.Type = 'TOWNHOUSE'
    AND h.Size = 'Medium'
)
OR
EXISTS
(
    SELECT 1 FROM Color c
    WHERE p.ID = c.PersonID
    AND (c.Foreground ='Green' or c.Foreground='Blue' or  c.Foreground='Purple')
)
);

這也會更好：

SELECT 
    p.*
FROM Person p
Left join House h
    On (p.Id=h.PersonID)
Left join Color c
    On (p.id=c.PersonID)
WHERE Substring(Ltrim(Rtrim(p.ZipCode)),1,3) = '123' AND p.City = 'Washington'AND 
(p.NumberOfHomes=1 or  p.NumberOfHomes=2 or p.NumberOfHomes=3)) and Isnull(h.Type,'') =   'TOWNHOUSE' AND Isnull(h.Size,'') = 'Medium' AND 
(Isnull(c.Foreground,'') ='Green' or Isnull(c.Foreground,'')='Blue' or Isnull(c.Foreground,'')='Purple') and 
(h.PersonID is not null or  c.PersonID is not null);

Answer 4

通常優化和具有多個不同的select語句是不同的主題，因為查詢優化器（SQL Server）通常會采用您的sql語句並以它認為最合適的方式運行它。

說這是肯定的幾種不同的方法，你可以把你的語句和它們組合成一個sql語句這里是一個例子。 這將保留您的人員表並從符合您條件的House或Color表中獲取匹配。

<!-- language:SQL-->
SELECT *
FROM Person Left Outer Join House ON Person.ID = House.PersonID Left Outer Join Color ON
Person.ID= Color.PersonID
WHERE (ZipCode LIKE '123%'
    AND City = 'Washington'
    AND Person.NumberofHomes in (1, 2, 3) )
    AND (
        House.Type = 'TOWNHOUSE'
        AND House.Size = 'Medium'
    )
    OR(
         Color.Foreground IN ('Green', 'Blue', 'Purple')
    )

我建議你重新考慮你的模型。 例如，具有顏色的PersonID是非常可疑的，因為具有numberofhomes（例如，可能可以通過House表上具有該人的id的計數來計算）。 還有一些其他可疑的規范化屬性。 不是你問題的一部分，但我認為你可能想要考慮它。