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SQL：查询学习笔记

發(fā)布時間：2025/5/22 数据库 40 豆豆

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SQL 查詢命令

SELECT

語法

SELECT "column_name"

FROM "table_name";

返回一列

1 SELECT Username FROM Users

返回多列

1 SELECT Username, Password From Users

返回所有列

1 SELECT * FROM Users

DISTINCT

語法

SELECT DISTINCT "column_name"

FROM "table_name";

示例

1 SELECT DISTINCT Name FROM Users

WHERE

語法

SELECT "column_name"
FROM "table_name"
WHERE "condition";

示例

1 SELECT * FROM Users WHERE Username = ‘HappyFramework’

AND OR

語法

SELECT "column_name"
FROM "table_name"
WHERE "simple condition"
{ [AND|OR] "simple condition"}+;

AND 示例

1 SELECT * FROM Orders Where Sales >= 1000 AND Sales <= 5000

OR 示例

1 SELECT * FROM Orders Where Sales < 1000 OR Sales > 5000

IN

語法

SELECT "column_name"
FROM "table_name"
WHERE "column_name" IN ('value1', 'value2', ...);

示例

1 SELECT * FROM Users WHERE Username IN (Happyframework, shijiucha)

BETWEEN

語法

SELECT "column_name"
FROM "table_name"
WHERE "column_name" BETWEEN 'value1' AND 'value2';

示例

1 SELECT * FROM Orders WHERE Sales BETWEEN 1000 AND 5000

LIKE

語法

SELECT "column_name"
FROM "table_name"
WHERE "column_name" LIKE {PATTERN};

% 示例

1 SELECT * FROM Users WHERE Name LIKE '%光'

_ 示例

1 SELECT * FROM Users WHERE Name LIKE '段光_'

ORDER BY

語法

SELECT "column_name"
FROM "table_name"
[WHERE "condition"]
ORDER BY "column_name" [ASC, DESC] {, "column_name" [ASC, DESC]}+;

示例

1 SELECT * FROM Users ORDER BY Username ASC

帶公式的示例

1 SELECT * FROM Orders ORDER BY Receipt - Refund

AVG

語法

SELECT AVG("column_name")
FROM "table_name";

示例

1 SELECT AVG(Sales) FROM Sales

COUNT

語法

SELECT COUNT("column_name")
FROM "table_name";

示例

1 SELECT COUNT(DISTINCT *) FROM Sales

MAX

語法

SELECT MAX ("column_name")
FROM "table_name";

示例

1 SELECT MAX(Sales) FROM Sales

MIN

語法

SELECT MIN ("column_name")
FROM "table_name";

示例

1 SELECT MIN(Sales) FROM Sales

SUM

語法

SELECT SUM ("column_name")
FROM "table_name";

示例

1 SELECT SUM(Sales) FROM Sales

GROUP BY

語法

SELECT "column_name1", "column_name2", ... "column_nameN", Function("column_nameN+1")
FROM "table_name"
GROUP BY "column_name1", "column_name2", ... "column_nameN";

示例

1 SELECT Customer, SUM(Sales) FROM Orders GROUP BY Customer

Having

語法

SELECT ["column_name1"], Function("column_name2")
FROM "table_name"
[GROUP BY "column_name1"]
HAVING (arithmetic function condition);

示例

1 SELECT Customer, SUM(Sales) 2 FROM Orders 3 GROUP BY Customer 4 HAVING SUM(Sales) > 10000

ALIAS

語法

SELECT "table_alias"."column_name1" "column_alias"
FROM "table_name" "table_alias";

示例

1 SELECT U.Username 用戶名 FROM Users U

AS

語法

SELECT "table_alias"."column_name1" "column_alias"
FROM "table_name" "table_alias";

示例

1 SELECT U.Username AS 用戶名 FROM Users AS U

INNER JOIN

語法

SELECT "column_name"
FROM "left_table_name"
INNER JOIN "right_table_name" ON "left_table_name"."left_column" = "right_table_name"."right_column";

示例

1 SELECT Categories.Name, News.Content 2 FROM News 3 INNER JOIN Categories ON News.CategoryId = Categories.Id

OUTER JOIN

語法

SELECT "column_name"
FROM "left_table_name"
OUTER JOIN "right_table_name" ON?"left_table_name"."left_column" =?"right_table_name"."right_column";

示例

1 SELECT Categories.Name, News.Content 2 FROM News 3 OUTER JOIN Categories ON News.CategoryId = Categories.Id

LEFT OUTER JOIN

語法

SELECT "column_name"
FROM "left_table_name"
LEFT OUTER JOIN "right_table_name" ON?"left_table_name"."left_column" =?"right_table_name"."right_column";

示例

1 SELECT Categories.Name, News.Content 2 FROM News 3 LEFT OUTER JOIN Categories ON News.CategoryId = Categories.Id

RIGHT OUTER JOIN

語法

SELECT "column_name"
FROM "left_table_name"
RIGHT OUTER JOIN "right_table_name" ON?"left_table_name"."left_column" =?"right_table_name"."right_column";

示例

1 SELECT Categories.Name, News.Content 2 FROM News 3 RIGHT OUTER JOIN Categories ON News.CategoryId = Categories.Id

CROSS JOIN

語法

SELECT "column_name"
FROM "left_table_name",?"right_table_name";

示例

1 SELECT Categories.Name, News.Content 2 FROM News, Categories

UNION

語法

[SQL Statement 1]
UNION
[SQL Statement 2];

示例

1 SELECT Name FROM Users 2 UNION 3 SELECT * FROM Employees

UNION ALL

語法

[SQL Statement 1]
UNION ALL
[SQL Statement 2];

示例

1 SELECT Name FROM Users 2 UNION ALL 3 SELECT * FROM Employees

INLINE VIEW

語法

SELECT "column_name" FROM (Inline View);

示例

1 SELECT * FROM 2 (SELECT * FROM Users)

INTERSECT

語法

[SQL Statement 1]
INTERSECT
[SQL Statement 2];

示例

1 SELECT Txn_Date FROM Store_Information 2 INTERSECT 3 SELECT Txn_Date FROM Internet_Sales;

MINUS

語法

[SQL Statement 1]
INTERSECT
[SQL Statement 2];

示例

1 SELECT Txn_Date FROM Store_Information 2 MINUS 3 SELECT Txn_Date FROM Internet_Sales;

TOP

語法

SELECT TOP N [PERCENT] "column_name"
FROM "table_name";

示例

1 SELECT TOP 2 Store_Name, Sales, Txn_Date 2 FROM Store_Information 3 ORDER BY Sales DESC;

百分比示例

1 SELECT TOP 25 PERCENT Store_Name, Sales, Txn_Date 2 FROM Store_Information 3 ORDER BY Sales DESC;

SUBQUERY

語法

1 SELECT "column_name1" 2 FROM "table_name1" 3 WHERE "column_name2" [Comparison Operator] 4 (SELECT "column_name3" 5 FROM "table_name2" 6 WHERE "condition");

示例

1 SELECT SUM (Sales) FROM Store_Information 2 WHERE Store_Name IN 3 (SELECT Store_Name FROM Geography 4 WHERE Region_Name = 'West'); 1 SELECT SUM (a1.Sales) FROM Store_Information a1 2 WHERE a1.Store_Name IN 3 (SELECT Store_Name FROM Geography a2 4 WHERE a2.Store_Name = a1.Store_Name);

EXISTS

語法

SELECT "column_name1"
FROM "table_name1"
WHERE EXISTS
(SELECT *
FROM "table_name2"
WHERE "condition");

示例

1 SELECT * 2 FROM Users 3 WHERE EXISTS (SELECT * FROM UserRoleRelations WHERE Users.Id = UserRoleRelations.UserId)

SIMPLE CASE

語法

SELECT CASE ("column_name")
WHEN "value1" THEN "result1"
WHEN "value2" THEN "result2"
...
[ELSE "resultN"]
END
FROM "table_name";

示例

1 SELECT Username, CASE (UserType) 2 WHEN 1 THEN "管理員" 3 WHEN 2 THEN "員工" 4 ELSE "未知" 5 FROM Users

SEARCHED CASE

語法

SELECT CASE
WHEN "condition1" THEN "result1"
WHEN "condition2" THEN "result2"
...
[ELSE "resultN"]
END
FROM "table_name";

示例

1 SELECT Username, CASE 2 WHEN UserType = 1 THEN "管理員" 3 WHEN UserType = 2 THEN "員工" 4 ELSE "未知" 5 FROM Users

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