sql自定義變量的基本用法

1.employee表 按 salary進行排名,相同的排名相同,並且排名連續: sql: SELECT @num := IF(@salary = salary, @num, @num + 1) num, //另@num重新賦值(如果@salary = 當前記錄的salary,@num賦值爲@num,否則賦值爲@num+1 ) @salary := salary salary FROM emplo

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