SQL Fuzzy Query Technology

Fuzzy query is a very common and useful query technique, which is necessary for beginners to master

General Fuzzy query statements are as follows:

SELECT field from table WHERE a field like condition

With regard to the conditions, SQL provides four matching modes:

1,%: Represents any 0 or more characters. Can match any type and length of the character, in some cases, if Chinese, please use two percent sign (%).

For example SELECT * from [user] WHERE u_name like '% three '

will be u_name for "Zhang San", "Zhang Cat Three", "three-legged Cat", "Tang Sanzang" and so on Have "three" records all find out.

Also, if you need to find a record of "three" and "cat" in U_name, use the and condition
SELECT * FROM [user] WHERE u_name like '% three ' and u_name like '% cat% '

If using SELECT * from [user] WHERE u_name like '% cat% '
Although can search out "three feet cat", but can not search out the eligible "Zhang Cat three".

2,_: Represents any single character. Matches a single arbitrary character, which is commonly used to restrict the expression's character-length statement:

For example SELECT * from [user] WHERE u_name like ' _ Three _ '
Only find "Tang Sanzang" so u_name for three words and the middle of a word is "three";

Another example is SELECT * from [user] WHERE u_name like ' three __ ';
Just find out "three-legged cat" this name is three words and the first word is "three";


3,[]: represents one of the characters listed in parentheses (similar to a regular expression). Specifies a character, string, or range that requires matching objects to be any of them.

such as SELECT * from [user] WHERE u_name like ' [Zhang Li Wang] three '
Will find "Zhang San", "Lie Triple", "Wang San" (not "Zhangli Kang");

such as [] a series of characters (01234, ABCDE, etc.) can be slightly written as "0-4", "A-E"
SELECT * FROM [user] WHERE u_name like ' old [1-9] '
Will find "Old 1", "Old 2" 、......、 "Old 9";

4,[^]: Represents a single character that is not listed within the parentheses. The value is the same as [], but it requires that the matched object be any character other than the specified character.

such as SELECT * from [user] WHERE u_name like ' [^ Zhang Li Wang] three '
Will find the surname "Zhang", "Li", "Wang" "Zhao Three", "Magozo" and so on;

SELECT * FROM [user] WHERE u_name like ' old [^1-4] ';
Will exclude "old 1" to "Old 4", Looking for "old 5", "Old 6" 、......

5, when the query contains a wildcard character

Because of the wildcard character, which causes us to query the special characters "%", "_", "[" the statement can not be implemented normally, and the special characters with "[]" in the normal query. Thus we write the following function:

function Sqlencode (str) Str=replace (str, "[", "[[]") ' This sentence must be in the top Str=replace (str, "_", "[_]") Str=replace (str, "%", "[%]") Sqlencode=str End Function

The following sentence query string is I wrote before, according to the variable in the ZIP Code table zipcode Query the corresponding data, this sentence is the judgment variable Zipcode_key is not a number when the query statement, with% to match any length of the string, from the table address, city, province three columns to query all data items containing the keyword , and sorted by province, city, and address. This is a simple example, so you can write more complex query statements as long as you understand the method.

sql = "SELECT * from ZipCode where (address like '%" & zipcode_key & "% ') or (city like '%" & zipcode_key & "% ') or (province like '% "& zipcode_key &"% ') Order byprovince,city,address

SQL Fuzzy Query Technology