Database - Introduction to SQL - Discussion

Wildcards are used in SQL to match a string pattern. There are two types of wildcards: % (percent sign) represents zero, one, or more characters (underscore) represents exactly one character.

What is SQL -92?

These two wildcards are imp in SQL.

% called as a Like operator.

A is the right answer because in SQL-92 * and % both are used as identical wild card.

Why we called % and _ are wildcard?

We use count (*) to count rows where * is the wildcard.

Actually when we want to match substring then we use % or pair of % as:

'sql%' this will return all results which starts with sql.

'%sql' will result in returning all string ending with sql.

'%sql%' having substring as sql.

Where we use '_' for character as:

'_' will return result which contains only one character in string.

'_ _ _ _' will return strings with exactly 4 characters

'sql_ _ _' will result in string which have exactly 3 characters followed by sql. i.e - 'sqltbl' and so on.

In SQL, wildcard characters can be used in "LIKE" expressions; the percent sign (%) matches zero or more characters, and underscore (_) a single character.

I also agree with the answer of kiran that % is used for more dan one character match and _ is used for single character match.

Thanks kiran.