删除条件和子字符串需要很长时间的querry [英] Delete querry with where condition and substring takes long time

问题描述

嗨我使用子串删除查询



删除来自[table]的SUBSTRING（[field]，1，CHARINDEX（N'''，[字段]） - 1）= 7



查询循环数百万条记录，并且花费很长时间，调整查询的任何消息，（表格不包含索引或约束）

hi i have delete query using substring

delete From [table] where SUBSTRING([field],1,CHARINDEX(N'''',[field])-1) = 7

the query loops through millions of records,and takes long time,any sugesttion of tuning the query,(the table does not contain indexing or constrains)

推荐答案

您可以根据子串公式创建一个持久计算列，并将该列与数字7进行比较。如果您确定它，我会说它将子串输出的数字转换为int，这将再次使其更快。

You can create a persisted computed column based on the substring formula and compare that column as number 7. I would say if you are sure that it would be number cast the substring output to int, which will again make it faster.

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