SQL fuzzy query statement

SQL fuzzy query statement

The general fuzzy statement syntax is as follows:

SELECT 字段 FROM 表 WHERE 某字段 Like 条件

About the conditions, SQL provides There are four matching modes:

1, %: represents any 0 or more characters. Can match characters of any type and length. In some cases, if it is Chinese, please use two percent signs (%%) to express it.

SELECT * FROM [user] WHERE u_name LIKE '%三%'

will find all the records with "three" in u_name as "Zhang San", "Zhang Cat San", "Three-legged Cat", "Tang Sanzang", etc. In addition, if you need to find records with both "三" and "cat" in u_name, please use the and condition

SELECT * FROM [user] WHERE u_name LIKE '%三%' AND u_name LIKE '%猫%'

If you use

SELECT * FROM [user] WHERE u_name LIKE '%三%猫%'

, you can search for "三级" Cat", but the search for "Zhang Cat San" that meets the conditions cannot be found.

2, _: represents any single character. Matches a single arbitrary character. It is often used to limit the character length of expressions:

 SELECT * FROM [user] WHERE u_name LIKE '_三_'

Only find "Tang Sanzang" so that u_name is three characters and the middle character is "三" ;

SELECT * FROM [user] WHERE u_name LIKE '三__';

Only find "three-legged cat" whose name has three characters and the first character is "三";

3. [ ]: represents one of the characters listed in brackets (similar to a regular expression). Specify a character, string, or range, requiring the matched object to be any one of them.

SELECT * FROM [user] WHERE u_name LIKE '[张李王]三'

will find "Zhang San", "Li San", "Wang San" (instead of "Zhang Li Wang San");

Such as [ ] If there is a series of characters (01234, abcde, etc.), it can be abbreviated as "0-4", "a-e"

SELECT * FROM [user] WHERE u_name LIKE '老[1-9]'

will find "old 1", "old 2",... ..., "老9";

4, [^]: Indicates a single character not listed in brackets. Its value is the same as [], but it requires that the matched object is any character other than the specified character.

SELECT * FROM [user] WHERE u_name LIKE '[^张李王]三'

Will find "Zhao San", "Sun San", etc. whose surnames are not "Zhang", "Li", "Wang";

SELECT * FROM [user] WHERE u_name LIKE '老[^1-4]';

Will exclude "Old 1" to "Old 4" and search for "Old 5", "Old 6",...

5. When the query content contains wildcards

Due to wildcards, our query statements for special characters "%", "_", and "[" cannot be implemented normally. However, the special characters can be queried normally if they are enclosed in "[ ]". Based on this, we write the following function:

function sqlencode(str)
str=replace(str,"[","[[]") '此句一定要在最前
str=replace(str,"_","[_]")
str=replace(str,"%","[%]")
sqlencode=str
end function

Before querying, the string to be checked can be processed by this function.

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