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最新推荐文章于 2024-07-07 17:46:33 发布

最新推荐文章于 2024-07-07 17:46:33 发布 · 152 阅读

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本文介绍如何在SQL查询中使用UNION ALL操作来允许重复值的选择，并演示了如何利用LIKE子句中的[charlist]通配符选取特定条件的数据记录。此外，还介绍了如何仅删除表中的数据而保留表结构的方法。

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Note: The UNION operator selects only distinct values by default. To allow duplicate values, use UNION ALL.

Using the [charlist] Wildcard
Now we want to select the persons with a last name that starts with "b" or "s" or "p" from the "Persons" table.

We use the following SELECT statement:

SELECT * FROM Persons
WHERE LastName LIKE '[bsp]%' 或者取反 '[!bsp]%'

What if we only want to delete the data inside the table, and not the table itself?

Then, use the TRUNCATE TABLE statement:

TRUNCATE TABLE table_name