Sqlite 简明教程
SQLite - GROUP BY Clause
SQLite *GROUP BY * 子句与 SELECT 语句配合使用，可将相同数据整理到组中。
SQLite *GROUP BY * clause is used in collaboration with the SELECT statement to arrange identical data into groups.
GROUP BY 子句在 SELECT 语句中跟在 WHERE 子句后面，在 ORDER BY 子句之前。
GROUP BY clause follows the WHERE clause in a SELECT statement and precedes the ORDER BY clause.
Syntax
以下是 GROUP BY 子句的基本语法。GROUP BY 子句必须遵循 WHERE 子句中的条件，如果使用 ORDER BY 子句，它必须在 ORDER BY 子句之前。
Following is the basic syntax of GROUP BY clause. GROUP BY clause must follow the conditions in the WHERE clause and must precede ORDER BY clause if one is used.
SELECT column-list
FROM table_name
WHERE [ conditions ]
GROUP BY column1, column2....columnN
ORDER BY column1, column2....columnN您可以在 GROUP BY 子句中使用多个列。确保您用于分组的任何列都应该出现在列列表中。
You can use more than one column in the GROUP BY clause. Make sure whatever column you are using to group, that column should be available in the column-list.
Example
考虑具有以下记录的 COMPANY 表。
Consider COMPANY table with the following records.
ID NAME AGE ADDRESS SALARY
---------- ---------- ---------- ---------- ----------
1 Paul 32 California 20000.0
2 Allen 25 Texas 15000.0
3 Teddy 23 Norway 20000.0
4 Mark 25 Rich-Mond 65000.0
5 David 27 Texas 85000.0
6 Kim 22 South-Hall 45000.0
7 James 24 Houston 10000.0如果您想了解每位客户的总薪水，则 GROUP BY 查询如下所示 −
If you want to know the total amount of salary on each customer, then GROUP BY query will be as follows −
sqlite> SELECT NAME, SUM(SALARY) FROM COMPANY GROUP BY NAME;这会产生以下结果 −
This will produce the following result −
NAME SUM(SALARY)
---------- -----------
Allen 15000.0
David 85000.0
James 10000.0
Kim 45000.0
Mark 65000.0
Paul 20000.0
Teddy 20000.0现在，让我们使用以下 INSERT 语句在 COMPANY 表中创建三条记录。
Now, let us create three more records in COMPANY table using the following INSERT statements.
INSERT INTO COMPANY VALUES (8, 'Paul', 24, 'Houston', 20000.00 );
INSERT INTO COMPANY VALUES (9, 'James', 44, 'Norway', 5000.00 );
INSERT INTO COMPANY VALUES (10, 'James', 45, 'Texas', 5000.00 );现在，我们的表具有以下重复的记录。
Now, our table has the following records with duplicate names.
ID NAME AGE ADDRESS SALARY
---------- ---------- ---------- ---------- ----------
1 Paul 32 California 20000.0
2 Allen 25 Texas 15000.0
3 Teddy 23 Norway 20000.0
4 Mark 25 Rich-Mond 65000.0
5 David 27 Texas 85000.0
6 Kim 22 South-Hall 45000.0
7 James 24 Houston 10000.0
8 Paul 24 Houston 20000.0
9 James 44 Norway 5000.0
10 James 45 Texas 5000.0同样，让我们使用相同的语句按 NAME 列对所有记录进行分组，如下所示 −
Again, let us use the same statement to group-by all the records using NAME column as follows −
sqlite> SELECT NAME, SUM(SALARY) FROM COMPANY GROUP BY NAME ORDER BY NAME;这将产生以下结果。
This will produce the following result.
NAME SUM(SALARY)
---------- -----------
Allen 15000
David 85000
James 20000
Kim 45000
Mark 65000
Paul 40000
Teddy 20000让我们将 ORDER BY 子句与 GROUP BY 子句结合使用，如下所示 −
Let us use ORDER BY clause along with GROUP BY clause as follows −
sqlite> SELECT NAME, SUM(SALARY)
FROM COMPANY GROUP BY NAME ORDER BY NAME DESC;这将产生以下结果。
This will produce the following result.
NAME SUM(SALARY)
---------- -----------
Teddy 20000
Paul 40000
Mark 65000
Kim 45000
James 20000
David 85000
Allen 15000