查询得到我不明白的结果

Question

我有此查询，该查询必须返回Exercises.leerjaar = 1的所有内容，但他还向我提供了有关Exercises.leerjaar = 2的数据

我尝试使用IS NULL，但这不能完全解决问题

SELECT exercises.* FROM exercises WHERE exercises.leerjaar = 1 AND exercises.niveau = 1 OR exercises.niveau = 2 AND exercises.dimensie_id = 1

我期望的结果是

exercises.leerjaar = 1 AND exercises.niveau = 1 OR exercises.niveau = 2 AND exercises.dimensie_id = 1

但是我现在得到的结果是

exercises.leerjaar = 1 OR exercises.leerjaar = 2 AND exercises.niveau = 1 OR exercises.niveau = 2 AND exercises.dimensie_id = 1

Answer 1

WHERE exercises.leerjaar = 1 
 AND (exercises.niveau = 1 OR exercises.niveau = 2) 
 AND exercises.dimensie_id = 1

别忘了在您的“ OR”条件周围加上括号

PS：能否准确地告诉我们您需要什么作为响应数据？