Question

SELECT save AS 'Simpanan', owe AS 'Hutang'
FROM
(
SELECT t.amount AS save, NULL AS owe
FROM trans t JOIN category cat
ON t.category_id = cat.category_id
WHERE cat.category_id = 1
UNION ALL
SELECT NULL AS save, t.amount AS owe
FROM trans t JOIN category cat
ON t.category_id = cat.category_id
WHERE cat.category_id = 2
)

我一直在努力解决这个mysql查询问题。我想要实现的是，结果只有一行。目前，此查询输出2行，列中的某些字段为NULL。如何才能使它只输出1行：

Simpanan    Hutang  
500         200

看看这里：http://sqlfiddle.com/#!5/89973/30

Answer 1

如果您确定只有一个结果使用子查询。

class StylesController < ApplicationController

  def new
    @style = Style.new
  end

  def create
    # your code
  end

end

或者：

SELECT 
   (SELECT t.amount AS save
    FROM trans t JOIN category cat
    ON t.category_id = cat.category_id
    WHERE cat.category_id = 1) AS 'Simpanan',
    (SELECT t.amount AS owe
    FROM trans t JOIN category cat
    ON t.category_id = cat.category_id
    WHERE cat.category_id = 2) AS 'Hutang'

使用JOIN表进行mysql多次查询并将结果合并到1行

1 个答案: