THE WORLD'S LARGEST WEB DEVELOPER SITE

SQL 教程

SQL主页 SQL简介 SQL语法 SQL选择 SQL选择 Distinct SQL位置 SQL运算符 SQL排序依据 SQL插入 SQL空值 SQL更新 SQL删除 SQL选择 Top SQL最小和最大 SQL计数 SQL喜爱 SQL通配符 SQL输入 SQL之间 SQL别名 SQL连接 SQL输入ner Join SQL左联接 SQL右连接 SQL完全联接 SQL自连接 SQL联盟 SQL分组依据 SQL具有 SQL存在 SQL全部 SQL选择 Into SQL插入 Select SQL案例 SQL空函数 SQL存储过程 SQL注释

SQL 数据库

SQL创建数据库 SQL Drop DB SQL备份数据库 SQL创建表 SQL删除表 SQL变更表 SQL约束 SQL不为空 SQL唯一 SQL主键 SQL外键 SQL检查 SQL默认值 SQL输入dex SQL自动增量 SQL日期 SQL视图 SQL输入jection SQL托管

SQL 参考

SQL关键字 MySQL函数 SQL Server函数 MS Access功能 SQL运算符 SQL数据类型 SQL快速参考

SQL 示例

SQL 示例 SQL测验 SQL 练习 SQL证书

SQL关键字 参考


This SQL keywords reference contains the reserved words in SQL.


SQL关键字

Keyword Description
ADD Adds a column in an existing table
ADD CONSTRAINT Adds a constraint after a table is already created
ALTER Adds, deletes, or modifies columns in a table, or changes the data type of a column in a table
ALTER COLUMN Changes the data type of a column in a table
ALTER TABLE Adds, deletes, or modifies columns in a table
ALL Returns true if all of the subquery values meet the condition
AND Only includes rows where both conditions is true
ANY Returns true if any of the subquery values meet the condition
AS Renames a column or table with an alias
ASC Sorts the result set in ascending order
BACKUP DATABASE Creates a back up of an existing database
BETWEEN Selects values within a given range
CASE Creates different outputs based on conditions
CHECK A constraint that limits the value that can be placed in a column
COLUMN Changes the data type of a column or deletes a column in a table
CONSTRAINT Adds or deletes a constraint
CREATE Creates a database, index, view, table, or procedure
CREATE DATABASE Creates a new SQL database
CREATE INDEX Creates an index on a table (allows duplicate values)
CREATE OR REPLACE VIEW Updates a view
CREATE TABLE Creates a new table in the database
CREATE PROCEDURE Creates a stored procedure
CREATE UNIQUE INDEX Creates a unique index on a table (no duplicate values)
CREATE VIEW Creates a view based on the result set of a SELECT statement
DATABASE Creates or deletes an SQL database
DEFAULT A constraint that provides a default value for a column
DELETE Deletes rows from a table
DESC Sorts the result set in descending order
DISTINCT Selects only distinct (different) values
DROP Deletes a column, constraint, database, index, table, or view
DROP COLUMN Deletes a column in a table
DROP CONSTRAINT Deletes a UNIQUE, PRIMARY KEY, FOREIGN KEY, or CHECK constraint
DROP DATABASE Deletes an existing SQL database
DROP DEFAULT Deletes a DEFAULT constraint
DROP INDEX Deletes an index in a table
DROP TABLE Deletes an existing table in the database
DROP VIEW Deletes a view
EXEC Executes a stored procedure
EXISTS Tests for the existence of any record in a subquery
FOREIGN KEY A constraint that is a key used to link two tables together
FROM Specifies which table to select or delete data from
FULL OUTER JOIN Returns all rows when there is a match in either left table or right table
GROUP BY Groups the result set (used with aggregate functions: COUNT, MAX, MIN, SUM, AVG)
HAVING Used instead of WHERE with aggregate functions
IN Allows you to specify multiple values in a WHERE clause
INDEX Creates or deletes an index in a table
INNER JOIN Returns rows that have matching values in both tables
INSERT INTO Inserts new rows in a table
INSERT INTO SELECT Copies data from one table into another table
IS NULL Tests for empty values
IS NOT NULL Tests for non-empty values
JOIN Joins tables
LEFT JOIN Returns all rows from the left table, and the matching rows from the right table
LIKE Searches for a specified pattern in a column
LIMIT Specifies the number of records to return in the result set
NOT Only includes rows where a condition is not true
NOT NULL A constraint that enforces a column to not accept NULL values
OR Includes rows where either condition is true
ORDER BY Sorts the result set in ascending or descending order
OUTER JOIN Returns all rows when there is a match in either left table or right table
PRIMARY KEY A constraint that uniquely identifies each record in a database table
PROCEDURE A stored procedure
RIGHT JOIN Returns all rows from the right table, and the matching rows from the left table
ROWNUM Specifies the number of records to return in the result set
SELECT Selects data from a database
SELECT DISTINCT Selects only distinct (different) values
SELECT INTO Copies data from one table into a new table
SELECT TOP Specifies the number of records to return in the result set
SET Specifies which columns and values that should be updated in a table
TABLE Creates a table, or adds, deletes, or modifies columns in a table, or deletes a table or data inside a table
TOP Specifies the number of records to return in the result set
TRUNCATE TABLE Deletes the data inside a table, but not the table itself
UNION Combines the result set of two or more SELECT statements (only distinct values)
UNION ALL Combines the result set of two or more SELECT statements (allows duplicate values)
UNIQUE A constraint that ensures that all values in a column are unique
UPDATE Updates existing rows in a table
VALUES Specifies the values of an INSERT INTO statement
VIEW Creates, updates, or deletes a view
WHERE Filters a result set to include only records that fulfill a specified condition



W3Schools is optimized for learning, testing, and training. 示例 might be simplified to improve reading and basic understanding. Tutorials, references, and examples are constantly reviewed to avoid errors, but we cannot warrant full correctness of all content. While using this site, you agree to have read and accepted our terms of use, cookie and privacy policy. Copyright 1999-2020 by Refsnes Data. All Rights Reserved.
Powered by W3.CSS.

W3Schools.com