sql - 如何使用 Distinct 在查询选择中获取计数元素？

Question

SELECT DISTINCT 
           t1.name as t1_name, 
           t1.unit as t1_unit, 
           t1.id_producer_goods AS hi_id_producer_goods, 
          t2.name as t2_name 
FROM Table1 t1 
    left join Table2 t2 on t1.id_web_site=t2.id_web_site 
WHERE t1.id='23'

如何t1.name在它的查询中计数？

我检查代码：

SELECT DISTINCT 
           t1.name as t1_name,
           count(t1.name) as count,           
           t1.unit as t1_unit, 
           t1.id_producer_goods AS hi_id_producer_goods, 
           t2.name as t2_name 
FROM Table1 t1 
    left join Table2 t2 on t1.id_web_site=t2.id_web_site 
WHERE t1.id='23'

但它的代码有错误：

Column 'Table1.name' is invalid in the select list because
it is not contained in either an aggregate function or the GROUP BY clause.

我知道我写得不对，count(t1.name) as count,但是如何正确计数t1.name？

PS：查询得到具有唯一行的结果t1.name, t1.unit, t1.id_producer_goods, t2.name。计数t1.name应该显示所有计数每个元素t1.name。

Answer 1

你必须添加

GROUP BY t1.name,t1.unit,hi.id_producer_goods,t2.name 

每当您沿其他列使用聚合函数时，您必须为其余列添加 group by 子句。

对于这些，您可以删除不同的。Group by 将为您完成。