SQL学习——基本语法

Posted 2021-02-07 gisliuliang

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!!)