In a case insensitive database, in a table’s column that was case insensitive, the customer was using the data as case sensitive. You can also use NOT LIKE to test whether or not a string does not match a pattern.The other day, I had a problem with some data that I never dreamed I would ever see. The LIKE operator is an integral part of SQL, and you’ll encounter many scenarios where it will be the only option (or at least, the best option). That is not to say you shouldn’t use it at all. Using the % operator as a prefix can be particularly slow.
Queries that contain the LIKE operator can run a lot slower than other queries, and you should probably avoid using the LIKE operator unless you really need it. In our table, there are two rows with NULL in the Email column, but those aren’t returned here. The percentage ( %) wildcard matches anything – almost. Changing the escape character can therefore help in such situations. In such cases, you may find yourself having to “double-escape” these characters, which could become confusing. This can be especially handy when you need to use the backslash for other purposes, such as encoding special characters. In this case I assigned the asterisk ( *) as the escape character. You can do this with the ESCAPE argument. It’s possible to change the escape character. Now we only get one row – the row that contains the underscore as the second character. That’s where the escape character comes in.
It would have matched even if it was something else.īut what if we only wanted to match those email addresses that have an actual underscore as their second character? The fact that the first row contains an underscore for the second character is just a coincidence. In this case, it didn’t matter what the second character was – it matched any character. Here’s an example of what happens when we don’t escape an underscore: SELECT * FROM Owners Notice that Owner 2 (Bart) has an email address that contains an underscore. | OwnerId | FirstName | LastName | Phone | Email | Suppose we have the following table: SELECT * FROM Owners This will prevent them from being interpreted as wildcard characters. In such cases, you can use a backslash ( \) to escape these characters. Sometimes you may find yourself in the situation where you need to search for an underscore or a percentage sign. In this case, we matched pet names where the second character is an e. The underscore ( _) wildcard operator matches any single character. You can also use the LIKE operator against the result of date functions, such as DAYNAME(), MONTHNAME(), etc. Here’s an example that matches the year from a date: SELECT * Numeric arguments are coerced to binary strings. WHERE PetName LIKE 'F%' COLLATE utf8_bin WHERE PetName LIKE 'f%' COLLATE utf8_bin īut if we change it to an uppercase F: SELECT * Alternatively, you can use CAST() to coerce it to a binary string. However, we can force a case-sensitive match by using the COLLATE clause with a binary collation. Therefore, we can change the previous example to use a lowercase f, and still get the same result: SELECT * LIKE performs case-insensitive substring matches if the collation for the expression and pattern is case-insensitive. In this example, I used the LIKE operator in conjunction with the % wildcard operator to return pets whose name starts with the letter F.
Here’s an example to demonstrate how the LIKE operator works. | PetId | PetTypeId | OwnerId | PetName | DOB | Suppose we have the following table: SELECT * FROM Pets The syntax goes like this: expr LIKE pat Example It can be used as either a prefix or a suffix, and it can also be used in the middle of a string. Matches any string of zero or more characters. Those wildcard characters are explained in the following table. It returns either 1 (TRUE) or 0 (FALSE).Ī pattern can include regular characters, as well the % and _ wildcard characters.
It determines whether a specific character string matches a specified pattern. In MariaDB, the LIKE operator allows you to do pattern matching.
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