如何匹配SQL中的任何字母？

Question

I want to return rows where certain fields follow a particular pattern such as whether a particular character in a string is a letter or number. To test it out, I want to return fields where the first letter is any letter. I used this code.

SELECT * FROM sales WHERE `customerfirstname` like '[a-z]%';

It returns nothing. So I would think that the criteria is the first character is a letter and then any following characters do not matter. The following code works, but limits rows where the first character is an a.

SELECT * FROM sales WHERE `customerfirstname` like 'a%';

Am I not understanding pattern matching? Isn't it [az] or [AZ] or [0-9] for any letter or number? Also if I wanted to run this test on the second character in a string, wouldn't I use

SELECT * FROM `sales` WHERE `customerfirstname` like '_[a-z]%' 

This is for SQL and MySQL. I am doing this in phpmyadmin.

Answer 1

You want to use regular expressions:

SELECT s.* 
FROM sales s
WHERE s.customerfirstname REGEXP '^[a-zA-Z]';

Answer 2

This can be achieved with a regular expression.

SELECT * FROM sales WHERE REGEXP_LIKE(customerfirstname, '^[[:alpha:]]');

^ denotes the start of the string, while the [:alpha] character class matches any alphabetic character.

Just in case, here are a few others character classes that you may find useful :

• alnum : dlphanumeric characters
• digit : digit characters
• lower : lowercase alphabetic characters
• upper : uppercase alphabetic characters

See the mysql regexp docs for many more...