SQLite Like % and _

Question

I can't figure out what the underscore character does in an SQLite like statement. The wildcard character, %, is probably the same as in most other SQL databases.

So, what does the _ character do?

Coeternity

Answer 1

The underscore is also the same as in most other SQL databases and matches any single character (i.e. it is the same as . in a regular expression). From the fine manual:

An underscore ("_") in the LIKE pattern matches any single character in the string.

For example:

-- The '_' matches the single 'c'
sqlite> select 'pancakes' like 'pan_akes';
1
-- This would need '__' to match the 'ca', only one '_' fails.
sqlite> select 'pancakes' like 'pan_kes';
0
-- '___' also fails, one too many '_'.
sqlite> select 'pancakes' like 'pan___kes';
0

And just to make sure the results make sense: SQLite uses zero and one for booleans.

Gilud

Answer 2

It is standard SQL that in LIKE expressions:

• % matches any sequence of characters, including an empty one. It is equivalent to .* in a regular expression.
• _ matches a single character. It is equivalent to . in a regular expression.

• You can choose a character for escaping %, _ and itself itself with:

  ... WHERE expr LIKE 'a_b%c\\d\%\_' ESCAPE '\'
  

  This will match a×b×××c\d%_ or a×bc\d%_ but not abc\d%_ nor a×b×××cd%_.

Additionnally with SQLite you have the GLOB keyword which behaves exactly the same way, except that % becomes * and _ becomes ?.

Pat

Thank you, Benoit. I chose the other answer judging by time only. – Coeternity

This saved my life. I was looking how to escape '%' in SQLite queries. But I had to give '\\' to get it working, not just '\' (I was working on Javscript+WebSQL). Below query worked for me. SELECT * FROM offers WHERE title LIKE '%50\\%%' ESCAPE '\\' (this will return all offers with title having 50%) – Ussery

@Francisc, I think you were fair in the beginning to choose the answer according to the time, but this answer is more clear than the currently accepted answer. It would be a service to future users to make this the accepted answer. – Sirocco

SQLite's GLOB is not exactly the same as LIKE but with different symbols. It's always case-sensitive, doesn't allow ESCAPE, and also supports character classes and ranges. – Quandary

Answer 3

Addendum to @Benoit's answer:

The ESCAPE applies to the most recent LIKE expression, not all LIKE expressions. To escape all you must use ESCAPE multiple times, such as below.

WHERE foo LIKE '%bar^%%' ESCAPE '^' AND foo LIKE '%baz^_%' ESCAPE '^'

This predicate matches values of foo which contain bar%, or baz plus any character.

Miele

Answer 4

For the record, I use in XCode/Objective-C environment, '\' doesn't work. Use anything else instead...

C-style escapes using the backslash character are not supported because they are not standard SQL (https://www.sqlite.org/lang_expr.html)

Quadrilateral