SQL学习——基本语法

以下是一些主要的SQL语句的语法实例

SELECT(查询某列)
SELECT column_name(s)
FROM table_name

SELECT DISTINCT(消除重复的元组)
SELECT DISTINCT column_name(s)
FROM table_name

SELECT *    (查询表中的所有数据)
SELECT *
FROM table_name

WHERE(范围限定)    
SELECT column_name(s)
FROM table_name
WHERE column_name operator value

LIKE    (匹配查询,注意:有5种通配符)
SELECT column_name(s)
FROM table_name
WHERE column_name LIKE pattern

ORDER BY (排序:ASC升序,DESC降序)
SELECT column_name(s)
FROM table_name
ORDER BY column_name [ASC|DESC]

INNER JOIN(内连接)
SELECT column_name(s)
FROM table_name1
INNER JOIN table_name2 
ON table_name1.column_name=table_name2.column_name

LEFT JOIN    (左外连接)
SELECT column_name(s)
FROM table_name1
LEFT JOIN table_name2 
ON table_name1.column_name=table_name2.column_name

RIGHT JOIN(右外连接)
SELECT column_name(s)
FROM table_name1
RIGHT JOIN table_name2 
ON table_name1.column_name=table_name2.column_name

FULL JOIN    (全外连接)
SELECT column_name(s)
FROM table_name1
FULL JOIN table_name2 
ON table_name1.column_name=table_name2.column_name

INSERT INTO    (插入数据)
INSERT INTO table_name
VALUES (value1, value2, value3,....)
or
INSERT INTO table_name
(column1, column2, column3,...)
VALUES (value1, value2, value3,....)

UPDATE    (修改数据)
UPDATE table_name
SET column1=value, column2=value,...
WHERE some_column=some_value

DELETE (删除数据)
DELETE FROM table_name
WHERE some_column=some_value
or
DELETE FROM table_name 
(Note: Deletes the entire table!!)

DELETE * FROM table_name 
(Note: Deletes the entire table!!)

 

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