# SQL 中文速查表

结构化查询语言(Structured Query Language)简称SQL,是一种特殊目的的编程语言,是一种数据库查询和程序设计语言,用于存取数据以及查询、更新和管理关系数据库系统。

# SQL 语句用法的速查表。

# 查找数据的查询

SELECT: 用于从数据库中选择数据
SELECT * FROM table_name;
DISTINCT: 用于过滤掉重复的值并返回指定列的行
SELECT DISTINCT column_name;
WHERE: 用于过滤记录/SELECT column1, column2 FROM table_name WHERE condition;
SELECT * FROM table_name WHERE condition1 AND condition2;
SELECT * FROM table_name WHERE condition1 OR condition2;
SELECT * FROM table_name WHERE NOT condition;
SELECT * FROM table_name WHERE condition1 AND (condition2 OR condition3);
SELECT * FROM table_name WHERE EXISTS (SELECT column_name FROM table_name WHERE condition);
ORDER BY: 用于结果集的排序,升序(ASC)或者降序(DESCSELECT * FROM table_name ORDER BY column;
SELECT * FROM table_name ORDER BY column DESC;
SELECT * FROM table_name ORDER BY column1 ASC, column2 DESC;
SELECT TOP: 用于指定从表顶部返回的记录数
SELECT TOP number columns_names FROM table_name WHERE condition;
SELECT TOP percent columns_names FROM table_name WHERE condition;
并非所有数据库系统都支持SELECT TOP。 MySQL 中是LIMIT子句
SELECT column_names FROM table_name LIMIT offset, count;
LIKE: 用于搜索列中的特定模式,WHERE 子句中使用的运算符
% (percent sign) 是一个表示零个,一个或多个字符的通配符
_ (underscore) 是一个表示单个字符通配符
SELECT column_names FROM table_name WHERE column_name LIKE pattern;
LIKE ‘a%’ (查找任何以“a”开头的值)
LIKE%a’ (查找任何以“a”结尾的值)
LIKE%or%’ (查找任何包含“or”的值)
LIKE ‘_r%’ (查找任何第二位是“r”的值)
LIKE ‘a_%_%’ (查找任何以“a”开头且长度至少为3的值)
LIKE[a-c]%’(查找任何以“a”或“b”或“c”开头的值)
IN: 用于在 WHERE 子句中指定多个值的运算符
本质上,IN运算符是多个OR条件的简写
SELECT column_names FROM table_name WHERE column_name IN (value1, value2,);
SELECT column_names FROM table_name WHERE column_name IN (SELECT STATEMENT);
BETWEEN: 用于过滤给定范围的值的运算符
SELECT column_names FROM table_name WHERE column_name BETWEEN value1 AND value2;
SELECT * FROM Products WHERE (column_name BETWEEN value1 AND value2) AND NOT column_name2 IN (value3, value4);
SELECT * FROM Products WHERE column_name BETWEEN #01/07/1999# AND #03/12/1999#;
NULL: 代表一个字段没有值
SELECT * FROM table_name WHERE column_name IS NULL;
SELECT * FROM table_name WHERE column_name IS NOT NULL;
AS: 用于给表或者列分配别名
SELECT column_name AS alias_name FROM table_name;
SELECT column_name FROM table_name AS alias_name;
SELECT column_name AS alias_name1, column_name2 AS alias_name2;
SELECT column_name1, column_name2 +,+ column_name3 AS alias_name;
UNION: 用于组合两个或者多个 SELECT 语句的结果集的运算符
每个 SELECT 语句必须拥有相同的列数
列必须拥有相似的数据类型
每个 SELECT 语句中的列也必须具有相同的顺序
SELECT columns_names FROM table1 UNION SELECT column_name FROM table2;
UNION 仅允许选择不同的值, UNION ALL 允许重复
ANY|ALL: 用于检查 WHEREHAVING 子句中使用的子查询条件的运算符
ANY 如果任何子查询值满足条件,则返回 trueALL 如果所有子查询值都满足条件,则返回 trueSELECT columns_names FROM table1 WHERE column_name operator (ANY|ALL) (SELECT column_name FROMtable_name WHERE condition);
GROUP BY: 通常与聚合函数(COUNT,MAX,MIN,SUM,AVG)一起使用,用于将结果集分组为一列或多列
SELECT column_name1, COUNT(column_name2) FROM table_name WHERE condition GROUP BY column_name1 ORDER BY COUNT(column_name2) DESC;
HAVING: HAVING 子句指定 SELECT 语句应仅返回聚合值满足指定条件的行。它被添加到 SQL 语言中,因为WHERE关键字不能与聚合函数一起使用。
SELECT COUNT(column_name1), column_name2 FROM table GROUP BY column_name2 HAVINGCOUNT(column_name1) > 5;

# 修改数据的查询

INSERT INTO: 用于在表中插入新记录/INSERT INTO table_name (column1, column2) VALUES (value1, value2);
INSERT INTO table_name VALUES (value1, value2 …);
UPDATE: 用于修改表中的现有记录/UPDATE table_name SET column1 = value1, column2 = value2 WHERE condition;
UPDATE table_name SET column_name = value;
DELETE: 用于删除表中的现有记录/DELETE FROM table_name WHERE condition;
DELETE * FROM table_name;

# 聚合查询

COUNT: 返回出现次数
SELECT COUNT (DISTINCT column_name);
MIN() and MAX(): 返回所选列的最小/最大值
SELECT MIN (column_names) FROM table_name WHERE condition;
SELECT MAX (column_names) FROM table_name WHERE condition;
AVG(): 返回数字列的平均值
SELECT AVG (column_name) FROM table_name WHERE condition;
SUM(): 返回数值列的总和
SELECT SUM (column_name) FROM table_name WHERE condition;

# 连接查询

INNER JOIN: 内连接,返回在两张表中具有匹配值的记录
SELECT column_names FROM table1 INNER JOIN table2 ON table1.column_name=table2.column_name;
SELECT table1.column_name1, table2.column_name2, table3.column_name3 FROM ((table1 INNER JOIN table2 ONrelationship) INNER JOIN table3 ON relationship);
LEFT (OUTER) JOIN: 左外连接,返回左表(table1)中的所有记录,以及右表中的匹配记录(table2)
SELECT column_names FROM table1 LEFT JOIN table2 ON table1.column_name=table2.column_name;
RIGHT (OUTER) JOIN: 右外连接,返回右表(table2)中的所有记录,以及左表(table1)中匹配的记录
SELECT column_names FROM table1 RIGHT JOIN table2 ON table1.column_name=table2.column_name;
FULL (OUTER) JOIN: 全外连接,全连接是左右外连接的并集. 连接表包含被连接的表的所有记录, 如果缺少匹配的记录,NULL 填充。
SELECT column_names FROM table1 FULL OUTER JOIN table2 ON table1.column_name=table2.column_name;
Self JOIN: 自连接,表自身连接
SELECT column_names FROM table1 T1, table1 T2 WHERE condition;

# 视图查询

CREATE: 创建视图
CREATE VIEW view_name AS SELECT column1, column2 FROM table_name WHERE condition;
SELECT: 检索视图
SELECT * FROM view_name;
DROP: 删除视图
DROP VIEW view_name;

# 修改表的查询

ADD: 添加字段
ALTER TABLE table_name ADD column_name column_definition;
MODIFY: 修改字段数据类型
ALTER TABLE table_name MODIFY column_name column_type;
DROP: 删除字段
ALTER TABLE table_name DROP COLUMN column_name;