\(反斜杠)在 SQL 查询中是什么意思? [英] What does \ (backslash) mean in an SQL query?

问题描述

我有以下查询

SELECT txt1 FROM T1 WHERE txt1 LIKE '_a\%'

这会导致答案包含任何字符+a+\+ 吗?

will that result in answers that have any char+a+\+whatever?

Pa\pe 之类的东西是否有效?

is something like Pa\pe valid as a result?

Ca% 或 _a% 可能是有效答案吗?

are Ca% or _a% valid answers maybe?

\ 在 SQL 查询中如何正常运行??

how does \ behave normally inside an SQL query??

推荐答案

% 是匹配 LIKE 子句中零个或多个字符的通配符._ 是一个通配符，它​​恰好匹配 LIKE 子句中的一个字符.

% is a wildcard character that matches zero or more characters in a LIKE clause. _ is a wildcard character that maches exactly one character in a LIKE clause.

\ 是一种特殊字符，称为转义字符，表示应按字面解释紧跟其后的字符(用于单引号、通配符等).

\ is a special character known as an escape character that indicates that the character directly following it should be interpreted literally (useful for single quotes, wildcard characters, etc.).

例如:

SELECT txt1 FROM T1 WHERE txt1 LIKE '_a%'

将选择 txt1 值为 'xa1'、'xa taco'、'ya nothing' 等的记录

will select records with txt1 values of 'xa1', 'xa taco', 'ya anything really', etc.

现在假设您要实际搜索百分号.为此，您需要一个特殊字符来指示 % 不应 被视为通配符.例如:

Now let's say you want to actually search for the percent sign. In order to do this you need a special character that indicates % should not be treated as a wildcard. For example:

SELECT txt1 FROM T1 WHERE txt1 LIKE '_a\%'

将选择 txt1 值为 'ba%' 的记录(但没有别的).

will select records with txt1 values of 'ba%' (but nothing else).

最后，LIKE 子句通常会包含通配符(否则您可以只使用 = 而不是 LIKE).因此，您可能会看到包含 \%% 的查询.这里第一个百分号将被视为文字百分号，但第二个将被解释为通配符.例如:

Finally, a LIKE clause would typically contain a wildcard (otherwise you could just use = instead of LIKE). So you might see a query containing \%%. Here the first percent sign would be treated as a literal percent sign, but the second would be interpreted as a wildcard. For example:

SELECT txt1 FROM T1 WHERE txt1 LIKE '_a\%%'

将选择 txt1 值为 'da%something else'、'fa% taco'、'ma% bundle of tacos' 等的记录

will select records with txt1 values of 'da%something else', 'fa% taco', 'ma% bunch of tacos', etc.

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