Question

我编写了一个sql语句，只保留一个实例（最小id），其中有重复的product_codes。问题是该声明效率非常低，并且运行时间非常长，所以我希望有一种更有效的方法来编写它

数据集的结构如下：

id  product_code  cat_desc      product_desc  
1   2352345       423           COCA COLA   
2   8967896       457           FANTA   
3   6456466       435           SPARKLING WATER 
4   3562314       457           STILL WATER

陈述是：

DELETE
FROM raw_products_inter
WHERE id IN (SELECT id
             FROM raw_products_inter outer_table
             WHERE product_code IN (SELECT product_code
                                    FROM raw_products_inter
                                    GROUP BY 1
                                    HAVING COUNT(id) > 1)
             AND   id NOT IN (SELECT MIN(id)
                              FROM raw_products_inter inner_table
                              WHERE inner_table.product_code = outer_table.product_code))

Answer 1

您应该能够使用EXISTS条件提升性能：

DELETE 
  FROM raw_products_inter P
 WHERE EXISTS (
          SELECT *
            FROM raw_products_inter OP
           WHERE OP.product_code = P.product_code
             AND OP.id < P.id
       )

用于删除重复行的SQL

1 个答案: