[英]Refining MySQL select query using UNION and DISTINCT
我的php脚本中有一个查询未返回所需数据。 查询是
select distinct require_category from users_require
返回:
Diet
Experience
MeasurementsGain
MeasurementsLoss
MeasurementsMaintain
WeightGain
WeightLoss
WeightMaintain
Workout
但是我只想要
Diet
Experience
MeasurementsGain
WeightGain
Workout
我已经优化了我的mysql查询并返回了corect结果,但是我认为它的效率不够:
select distinct require_category from users_require where require_category NOT LIKE '%Weight%' and require_category NOT LIKE '%Measurements%' union select distinct require_category from users_require where require_category = 'WeightGain' or require_category = 'MeasurementsGain'
请尝试以下,
SELECT DISTINCT
require_category FROM users_require WHERE require_category NOT LIKE '%Loss%'
AND require_category NOT LIKE '%Maintain%'
你可以用一些工会
select min(require_category)
from users_require
where require_category like 'Measurements%';
union
select min(require_category)
from users_require
where require_category like 'Weigh%';
union
select require_category
from users_require
where require_category not like 'Measurements%'
and require_category not like 'Weigh%';
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