Sql server 使用内部联接更新到同一个表优化
查询是:Sql server 使用内部联接更新到同一个表优化,sql-server,Sql Server,查询是: CREATE TABLE logfile ( sequence_number BIGINT, start_time DECIMAL, finish_time DECIMAL, irp_major VARCHAR(100), offset BIGINT, length BIGINT, filename VARCHAR(2000), is_seq BIT ); //bulk insert 120 000 rows CREATE CLU
CREATE TABLE logfile (
sequence_number BIGINT,
start_time DECIMAL,
finish_time DECIMAL,
irp_major VARCHAR(100),
offset BIGINT,
length BIGINT,
filename VARCHAR(2000),
is_seq BIT
);
//bulk insert 120 000 rows
CREATE CLUSTERED INDEX IX_logfile ON logfile(sequence_number);
UPDATE dbo.logfile SET is_seq = (
SELECT CASE WHEN a.offset = (b.offset + b.length) THEN 1 ELSE 0 END AS seq
FROM dbo.logfile a
LEFT JOIN dbo.logfile b
ON a.sequence_number = b.sequence_number + 1
WHERE a.sequence_number = logfile.sequence_number)
我是否可以提高更新查询的性能 也许这个更新会更快
MERGE
INTO logfile l
USING (
SELECT sequence_number + 1 AS pseq,
p.*
FROM logfile p
) pl
ON l.sequence_number = pseq
WHEN MATCHED THEN
UPDATE
SET is_seq = CASE WHEN l.offset = (pl.offset + pl.length) THEN 1 ELSE 0 END
UPDATE dbo.LogFile SET is_seq = 0
UPDATE dbo.LogFile SET is_seq = 1
FROM dbo.LogFile f
INNER JOIN (
SELECT f2.sequence_number
FROM dbo.LogFile f1
INNER JOIN dbo.LogFile f2 ON f2.sequence_number = f1.sequence_number + 1
WHERE f1.Offset <> f2.Offset + f2.Length
) f2 ON f2.sequence_number = f.sequence_number
@卡西诺。不管结果如何,我又学到了一些新东西。Thx.ahh发现错误:序列号-1应该是序列号+1。现在效果很好,速度差不多相当于@lievens,两者都比我的好一个数量级: