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Hint : USE_CONCAT

原创 IT综合 作者:tsinglee 时间:2007-11-22 13:38:01 0 删除 编辑

/*+ USE_CONCAT */

Causes all ORs in the statement to be transferred to UNION ALLs.

Use the USE_CONCAT hint to change OR conditions into a UNION ALL. We have found that this hint does not always seem to work as expected. The OR EXISTS in the script below is one case where the USE_CONCAT would speed up the processing considerably.

SELECT /*+ USE_CONCAT */ a.acct_name
FROM accts a
WHERE a.acct_no between (1000 and 2000)
OR EXISTS
(SELECT 'x'
FROM trans t
WHERE a.acct_no = t.acct_no
AND t.trans_type='E');

[@more@]

来自 “ ITPUB博客 ” ,链接:http://blog.itpub.net/10599713/viewspace-983287/,如需转载,请注明出处,否则将追究法律责任。

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