mysql查询显示而不是NULL - 0

Question

我有这个查询

SELECT
A.cod_material,
SUM(B.cantidad_pedido) as cantidad_pedido
FROM materiales AS A LEFT JOIN ingreso_material AS B 
on A.cod_material = B.cod_material GROUP BY A.cod_material;  

我的结果是

cod_material    cantidad_pedido
--------------------------------
321010001             NULL
321010002             25125
321010004             1283
321010006             NULL

我希望它显示而不是NULL（0）

321010001               0

Ty为你提供帮助

Answer 1

使用case

SUM(case when B.cantidad_pedido IS NULL 
         then 0 
         else B.cantidad_pedido 
    end) as cantidad_pedido

或isnull

SUM(ISNULL(B.cantidad_pedido, 0)) as cantidad_pedido

Answer 2

在此处使用COALESCE()。该函数返回第一个非NULL值。

SELECT
  A.cod_material,
  COALESCE(SUM(B.cantidad_pedido), 0) as cantidad_pedido
FROM materiales AS A LEFT JOIN ingreso_material AS B 
  on A.cod_material = B.cod_material GROUP BY A.cod_material;