hql对数据库的查询语句
标题：HQL查询语句示例
1. 查询所有记录
```hql
SELECT * FROM table_name;
```
2. 查询指定字段的记录
```hql
SELECT column1, column2 FROM table_name;
```
3. 查询满足条件的记录
```hql
SELECT * FROM table_name WHERE condition;
```
4. 使用聚合函数查询数据
```hql
SELECT COUNT(*) FROM table_name;
SELECT SUM(column) FROM table_name;
SELECT AVG(column) FROM table_name;
SELECT MAX(column) FROM table_name;
SELECT MIN(column) FROM table_name;
```
5. 查询记录并按指定字段排序
```hql
SELECT * FROM table_name ORDER BY column ASC/DESC;
```
6. 查询记录并限制返回的行数
```hql
SELECT * FROM table_name LIMIT count;
```
7. 查询记录并分页显示
```hql
SELECT * FROM table_name LIMIT start, count;
```
8. 使用连接查询
```hql
SELECT * FROM table1 INNER JOIN table2 ON condition;
SELECT * FROM table1 LEFT JOIN table2 ON condition;
distinct查询SELECT * FROM table1 RIGHT JOIN table2 ON condition;
```
9. 使用子查询查询数据
```hql
SELECT column FROM table_name WHERE column IN (SELECT column FROM table_name WHERE condition);
SELECT column FROM (SELECT column FROM table_name WHERE condition) AS subquery;
```
10. 使用通配符进行模糊查询
```hql
SELECT * FROM table_name WHERE column LIKE pattern;
```
11. 使用GROUP BY进行分组查询
```hql
SELECT column, COUNT(*) FROM table_name GROUP BY column;
```
12. 使用HAVING进行分组条件过滤
```hql
SELECT column, COUNT(*) FROM table_name GROUP BY column HAVING condition;
```
13. 使用DISTINCT查询去重记录
```hql
SELECT DISTINCT column FROM table_name;
```
14. 使用CASE WHEN进行条件查询
```hql
SELECT column, CASE WHEN condition1 THEN result1 WHEN condition2 THEN result2 ELSE result3 END FROM table_name;
```
15. 使用BETWEEN进行范围查询
```hql
SELECT * FROM table_name WHERE column BETWEEN value1 AND value2;
```
16. 使用EXISTS进行关联查询
```hql
SELECT column FROM table1 WHERE EXISTS (SELECT column FROM table2 WHERE condition);
```
17. 使用UNION合并查询结果
```hql
SELECT column FROM table1 UNION SELECT column FROM table2;

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