聚类索引要不要加 order by
数据库要不要加order by给大家两个例子一看就知道了 view plaincopyCREATE TABLE Beatles (LastName varchar(20) NOT NULL PRIMARY KEY CLUSTERED, FirstName varchar(20) NOT NULL UNIQUE NONCLUSTERED); INSERT INTO Beatles (LastName, FirstName) SELECT 'Lennon', 'John' UNION ALL SELECT 'McCartney', 'Paul' UNION ALL SELECT 'Harrison', 'George' UNION ALL SELECT 'Starr', 'Ringo'; SELECT LastName FROM Beatles; DROP TABLE Beatles; go LastName -------------------- Harrison Lennon McCartneyStarr view plaincopyCREATE TABLE Stones (LastName varchar(20) NOT NULL PRIMARY KEY CLUSTERED, FirstName varchar(20) NOT NULL UNIQUE NONCLUSTERED); INSERT INTO Stones (LastName, FirstName) SELECT 'Jagger', 'Mick' UNION ALL SELECT 'Jones', 'Brian' UNION ALL SELECT 'Richards', 'Keith' UNION ALL SELECT 'Watts', 'Charlie' UNION ALL SELECT 'Wyman', 'Bill'; SELECT LastName FROM Stones; DROP TABLE Stones; go LastName -------------------- Wyman Jones Watts Richards Jagger 第一个表没有问题，输出即使没加 order by 也能按照正常输出，但是第二个表却是乱序，为什么那？http://my.csdn.net/uploads/201204/20/1334905364_5599.JPG
答案就在这个执行计划里，所以，无论何时不要忽略优化器的选择，要不然诡异的现象就会时有发生，另外你都已经有了聚类索引，多加一个order by会死人啊？效率会低啊？我说我自己。
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