字符串类:
CHAR(N),CHARACTER(n) 字符/字符串。固定长度 n。
VARCHAR(n),CHARACTER VARYING(n) 字符/字符串。可变长度。最大长度 n。
数字类:
BINARY(n) 二进制串,固定长度 n。
BOOLEAN 存储 TRUE 或 FALSE 值
VARBINARY(n) 或BINARY VARYING(n) 二进制串。可变长度。最大长度 n。
INT,INTEGER 长整数,4字节
SMALLINT 短整数,2字节
BIGINT 大整数,8字节
定点数:
NUMERIC(p,d) 定点数,有p为数字(不包含符号和小数点)组成,小数点后d位
DECIMAL(p,d),DEC(p,d) 同上
浮点数:
REAL 单精度浮点数,取决于机器精度
DOUBLR PRECISION双精度浮点数
FLOAT (n) 可选精度的浮点数
日期:
DATE 存储年、月、日的值。YYYY-MM-DD
TIME 存储小时、分、秒的值。HH:MM:SS
TIMESTAMP 存储年、月、日、小时、分、秒的值。
INTERVAL 由一些整数字段组成,代表一段时间,取决于区间的类型。
集合:
ARRAY 元素的固定长度的有序集合
MULTISET 元素的可变长度的无序集合
XML 存储 XML 数据
以下是引用
语句 | 语法 |
---|---|
AND / OR | SELECT column_name(s) FROM table_name WHERE condition AND|OR condition |
ALTER TABLE (add column) | ALTER TABLE table_name ADD column_name datatype |
ALTER TABLE (drop column) | ALTER TABLE table_name DROP COLUMN column_name |
AS (alias for column) | SELECT column_name AS column_alias FROM table_name |
AS (alias for table) | SELECT column_name FROM table_name AS table_alias |
BETWEEN | SELECT column_name(s) FROM table_name WHERE column_name BETWEEN value1 AND value2 |
CREATE DATABASE | CREATE DATABASE database_name |
CREATE INDEX | CREATE INDEX index_name ON table_name (column_name) |
CREATE TABLE | CREATE TABLE table_name ( column_name1 data_type, column_name2 data_type, ....... ) |
CREATE UNIQUE INDEX | CREATE UNIQUE INDEX index_name ON table_name (column_name) |
CREATE VIEW | CREATE VIEW view_name AS SELECT column_name(s) FROM table_name WHERE condition |
DELETE FROM | DELETE FROM table_name (Note: Deletes the entire table!!) or DELETE FROM table_name |
DROP DATABASE | DROP DATABASE database_name |
DROP INDEX | DROP INDEX table_name.index_name |
DROP TABLE | DROP TABLE table_name |
GROUP BY | SELECT column_name1,SUM(column_name2) FROM table_name GROUP BY column_name1 |
HAVING | SELECT column_name1,SUM(column_name2) FROM table_name GROUP BY column_name1 HAVING SUM(column_name2) condition value |
IN | SELECT column_name(s) FROM table_name WHERE column_name IN (value1,value2,..) |
INSERT INTO | INSERT INTO table_name VALUES (value1, value2,....) or INSERT INTO table_name |
LIKE | SELECT column_name(s) FROM table_name WHERE column_name LIKE pattern |
ORDER BY | SELECT column_name(s) FROM table_name ORDER BY column_name [ASC|DESC] |
SELECT | SELECT column_name(s) FROM table_name |
SELECT * | SELECT * FROM table_name |
SELECT DISTINCT | SELECT DISTINCT column_name(s) FROM table_name |
SELECT INTO (used to create backup copies of tables) | SELECT * INTO new_table_name FROM original_table_name or SELECT column_name(s) |
TRUNCATE TABLE (deletes only the data inside the table) | TRUNCATE TABLE table_name |
UPDATE | UPDATE table_name SET column_name=new_value [, column_name=new_value] WHERE column_name=some_value |
WHERE | SELECT column_name(s) FROM table_name WHERE condition |
搜索
如果绑定了指定数据库,可以直接用表名称。
如果有多个数据库情况下,应该用数据库名.表名称
,如学生课程管理系统.学生信息
,学生课程管理系统是数据库名,学生信息是表名称。
搜索全部
select * from 表名称
搜索指定属性名的信息
select 属性名(列名称) from 表名称
搜索满足条件表达式的所有数据
select * from 表名称 where 条件表达式
搜索满足条件的唯一的指定属性
select DISTINCT 属性名(列名称) from 表名称 where 条件表达式
条件表达式WHERE
操作符 | 描述 |
---|---|
= | 等于 |
<> | 不等于 |
> | 大于 |
< | 小于 |
>= | 大于等于 |
<= | 小于等于 |
BETWEEN | 在某个范围内 |
LIKE | 搜索某种模式 |
更多推荐
SQL 常用数据类型汇总
发布评论