Question

我的查询是这样的：

SELECT t1.customer_name, t1.total, t2.customer_name, t2.total,
       (t1.total - t2.total) as var_1
FROM topuserslcy t1, topuserslcy t2
WHERE t1.report_date = '2015-12-22' AND
      t2.report_date = '2015-12-23' AND var_1 > 0;

我希望它只选择值或var_1为正或大于零的行。 Thnaks

Answer 1

您不能在from子句中使用列别名。我强烈怀疑你需要适当的join条件。。。作为一般规则，从不在from子句中使用逗号。

MySQL具有允许在having子句中使用别名的功能。因此，如果编写为：

，您的查询将会运行

SELECT t1.customer_name, t1.total, t2.customer_name, t2.total,
       (t1.total - t2.total) as var_1
FROM topuserslcy t1 CROSS JOIN
     topuserslcy t2
WHERE t1.report_date = '2015-12-22' AND
      t2.report_date = '2015-12-23' 
HAVING var_1 > 0;

Answer 2

ANSI SQL兼容的答案，使用派生表。检查顶级var_1：

select * from
(
SELECT t1.customer_name, t1.total, t2.customer_name, t2.total,
       (t1.total - t2.total) as var_1
FROM topuserslcy t1, topuserslcy t2
WHERE t1.report_date = '2015-12-22' AND
      t2.report_date = '2015-12-23'
) dt
WHERE var_1 > 0;

（但为什么没有JOIN条件？）

Answer 3

试试这个：

SELECT temp.* FROM (SELECT t1.customer_name, t1.total, t2.customer_name, t2.total,
       (t1.total - t2.total) as var_1
FROM topuserslcy t1, topuserslcy t2
WHERE t1.report_date = '2015-12-22' AND
      t2.report_date = '2015-12-23') as temp WHERE temp.var_1 > 0;

sql选择与评估条件匹配的行

3 个答案: