Wildcard underscore “_” :

“_” helps to match exactly one character.

Ex. select name from name_table where name like “c_p”

The above query will return words such as “cap”, “cop”, “cup” or basically anything which is a three letter word starting with the letter “c” and ending with “p”.

Wildcard “%” :

“%” helps match any number of characters. Let’s take the same example as above:

select name from name_table where name like “c%p”

The output can be “cap”, “cop” and can also be “coooop”, “caawjshygfvsbchjsp” etc etc.

So what basically happens with “%” is that it will include any number of characters whereas “_” will include only one character.

Ex. If you want to insert the name D’souza into MS SQL the query goes like this:

INSERT into name_column ([name]) VALUES (‘D”Souza’)

Look carefully. We have replaced single quote in between the letter D and the word SOUZA with two SINGLE QUOTES. (It’s not a double quote)

Similarly, you may also face a problem while querying for values which contain the characters ‘%’ and ‘_’ in them. This is so because SQL considers these two characters as wild cards for multiple characters and single character string matching.

There are 2 ways to escape these wild cards.

1. You can use the default square braces “[]” like this- [%] or [_]

2. You can define your own escape character by using the keyword ESCAPE at the end of your where clause.

Ex. select * from name_column where name like ‘gyan\_sagar’ ESCAPE ‘\’

In the example above we escape “_” by defining “\” as an escape character using the ESCAPE keyword.

Note: You can only define a single character for escaping and not a string.

I hope this post has made your work a bit more easier than before. Your suggestions and comments are always welcome.