SQL 去重的写法

1. 使用DISTINCT关键字

SELECT DISTINCT column_name FROM table_name;

2. 使用GROUP BY语句

SELECT column_name FROM table_name GROUP BY column_name;

3. 使用子查询

SELECT column_name FROM (SELECT DISTINCT column_name FROM table_name) AS temp_table;

4. 使用ROW_NUMBER()函数

SELECT column_name FROM (SELECT ROW_NUMBER() OVER (PARTITION BY column_name ORDER BY column_name) AS row_num, column_name FROM table_name) AS temp_table WHERE row_num = 1;

5. 使用EXISTS子查询

SELECT column_name FROM table_name t1 WHERE NOT EXISTS (SELECT 1 FROM table_name t2 WHERE t2.column_name = t1.column_name AND t2.id < t1.id)