mysql - 如果任一表中的特定日期，如何从两个表中返回单个记录

Question

我有两个表，每个表都有一个日期字段。如果 EITHER 表有特定日期，则仅返回相应表中的单个记录。这很接近，但它总是返回两个表:

SELECT ruberic.teacherid,
       ruberic.date,
       coaching_interactions.teacherid,
       coaching_interactions.date
FROM   ruberic,
       coaching_interactions
WHERE  ruberic.date = '2016-12-13'
        OR coaching_interactions.date = '2016-12-13'

Answer 1

您可以使用 Union .它还将删除重复项(如果有):

SELECT ruberic.teacherid,
       ruberic.date,
FROM   ruberic 
WHERE  ruberic.date = '2016-12-13'

UNION 

SELECT coaching_interactions.teacherid,
       coaching_interactions.date
FROM   coaching_interactions
WHERE  coaching_interactions.date = '2016-12-13'