摘要：关系运算符： ±：\pm ×：\times ÷：\div ∣：\mid ∤：\nmid ⋅：\cdot ∘：\circ ∗：\ast ⨀：\bigodot ⨂：\bigotimes ⨁：\bigoplus ≤：\leq ≥：\geq ≠：\neq ≈：\approx ≡：\equiv ∑：\sum 阅读全文

摘要：在表中分别统计mt =0 和 mt>0 的个数 方法一：select count(if(mt=0,1,null)) as a,count(if(mt>0,1,null)) as b from table 方法二：select sum(mt=0) as a,sum(mt>0) as b from ta 阅读全文