sql基础笔试题

sql基础笔试题含解答共20道
1. 查询所有表名
```sql
--解答
SHOW TABLES;
```
2. 查询表中所有列名和数据类型
```sql
--解答
DESCRIBE table_name;
```
3. 查询表中所有数据
```sql
--解答
SELECT * FROM table_name;
```
4. 查询表中满足条件的数据
```sql
--解答
SELECT * FROM table_name WHERE column_name = 'value';
```
5. 查询表中指定列的数据
```sql
--解答
SELECT column1, column2 FROM table_name;
```
6. 查询表中数据的总行数
```sql
--解答
SELECT COUNT(*) FROM table_name;
```
7. 查询表中数据的平均值
```sql
--解答
SELECT AVG(column_name) FROM table_name;
```
8. 查询表中数据的最大值和最小值
```sql
--解答
SELECT MAX(column_name), MIN(column_name) FROM table_name;
```
9. 查询表中数据的总和
```sql
--解答
SELECT SUM(column_name) FROM table_name;
```
10. 查询表中去重后的数据
```sql
--解答
SELECT DISTINCT column_name FROM table_name;
```
11. 查询表中数据按某列升序排序
```sql
--解答
SELECT * FROM table_name ORDER BY column_name ASC;
```
12. 查询表中数据按某列降序排序
```sql
--解答
SELECT * FROM table_name ORDER BY column_name DESC;
```
13. 查询表中指定范围的数据
```sql
--解答
SELECT * FROM table_name WHERE column_name BETWEEN value1 AND value2; ```
14. 插入数据
```sql
--解答
INSERT INTO table_name (column1, column2) VALUES ('value1', 'value2');
```
15. 更新数据
```sql
--解答
UPDATE table_name SET column_name = 'new_value' WHERE condition;
```
16. 删除数据
```sql
--解答
DELETE FROM table_name WHERE condition;
```
17. 使用聚合函数计算分组后的数据
```sql
--解答
SELECT column_name, COUNT(*) FROM table_name GROUP BY column_name;
```
18. 使用JOIN进行表连接查询
```sql
--解答
SELECT * FROM table1 JOIN table2 ON table1.column_name = table2.column_name;
```
19. 使用子查询
```sql
--解答
SELECT column_name FROM table_name WHERE column_name IN (SELECT column_name FROM another_table);
```
20. 创建新表
```sql
--解答
CREATE TABLE new_table AS SELECT * FROM old_table;
```。