SQL学习笔记
DML
SELECT UPDATE DELETE INSERT INTO
DDL
CREATE DATABASE ALTER DATABASE CREATE TABLE ALTER TABLE DROP TABLE CREATE INDEX DROP INDEX
DISTINCT
SELECT Company FROM Orders| Company |
|---|
| a |
| b |
| a |
SELECT DISTINCT Company FROM Orders| Company |
|---|
| a |
| b |
WHERE
| 操作符 |
|---|
| <> 不等于 |
| BETWEEN 在某个范围内 |
| LIKE 搜索某种模式 |
- Tip: SQL 使用单引号来环绕文本值（大部分数据库系统也接受双引号
ORDER BY
SELECT * FROM Orders ORDER BY Company先按Company字母顺序优先，遇到字母相同的再按数字优先！
SELECT * FROM Orders ORDER BY Company,OrderNumber降序
SELECT * FROM Orders ORDER BY Company DESC升序降序
SELECT * FROM Orders ORDER BY Compant DESC, OrderNumber ASCINSERT INTO
注意这里Persons表里列名Address和City不用加引号
INSERT INTO Persons (Address,City) VALUES ('XXX','XXX')UPDATE
UPDATE Persons SET Address='xxx' WHERE City='xxx'DELETE
用于删除行
DELETE FROM Persons WHERE City='XXX'TOP
SELECT *
FROM Persons
LIMIT 5