1.?一句話實(shí)現(xiàn)Mysql查詢結(jié)果帶行號(hào)? ?

SELECT @rowno:=@rowno+1 AS rowno,a.id,a.`status`,a.reason FROM e_four_auth a,(SELECT @rowno:=0) b

?(SELECT @rowno:=0) 初始化rowno? ?； @rowno:=@rowno+1 每行+1

2.explain?用法和結(jié)果的含義

1 inner join :?SELECT * FROM TableA INNER JOIN TableB ON TableA.name = TableB.name?

交集

2?left join :?SELECT * FROM TableA LEFT JOIN TableB ON TableA.name = TableB.name

A的完全集，B中能匹配的則有值，沒有匹配的則null. (right left類似。不寫了)

SELECT * FROM TableA LEFT JOIN TableB ON TableA.name = TableB.name WHERE TableB.id IS NULL;

A中有，B中沒有的