I am using glob operator with "?" wildcharater.The problem is - it is case sensitive.
So suppose I want to search for "Hola", then below query does not work.
select * from tableName where columnName glob 'ho?a';
I can use LOWER or UPPER keywords with columnName , but then it also it fails for the text which is a combination of lower and upper case letters.
Please give your inputs.
GLOB is case sensitive by design.
If you want case insensitive matching, use LIKE, with _ matching a single character:
select * from tableName where columnName like 'ho_a';
GLOB supports character classes:
SELECT * FROM tableName WHERE columnName GLOB '[hH][oO]?[aA]';
However, using LIKE would be easier, unless you actually need to use character classes in some other part of the pattern.
Related
Is it possible to write a query which searches for non-space, non-letter and non-digit characters in a column? I need to check if there are any chars like minus, apostrophes and so on.
SELECT * FROM MyTable WHERE MyCol "has at least one letter which is not A-Z, a-z or 0-9";
You can't really do this easily without regex support. If your version of SQLite supports REGEXP, then it provides one way:
SELECT *
FROM MyTable
WHERE MyCol REGEXP '[^A-Za-z0-9 ]';
How performant is the SQLite3 REGEXP operator?
For simplicity, assume a simple table with a single column pattern and an index
CREATE TABLE `foobar` (`pattern` TEXT);
CREATE UNIQUE INDEX `foobar_index` ON `foobar`(`pattern`);
and a query like
SELECT * FROM `foobar` WHERE `pattern` REGEXP 'foo.*'
I have been trying to compare and understand the output from EXPLAIN and it seems to be similar to using LIKE except it will be using regexp for matching. However, I am not fully sure how to read the output from EXPLAIN and I'm not getting a grasp of how performant it will be.
I understand it will be slow compared to a indexed WHERE `pattern` = 'foo' query but is it slower/similar to LIKE?
sqlite does not optimize WHERE ... REGEXP ... to use indexes. x REGEXP y is simply a function call; it's equivalent to regexp(x,y). Also note that not all installations of sqlite have a regexp function defined so using it (or the REGEXP operator) is not very portable. LIKE/GLOB on the other hand can take advantage of indexes for prefix queries provided that some additional conditions are met:
The right-hand side of the LIKE or GLOB must be either a string literal or a parameter bound to a string literal that does not begin with a wildcard character.
It must not be possible to make the LIKE or GLOB operator true by having a numeric value (instead of a string or blob) on the left-hand side. This means that either:
the left-hand side of the LIKE or GLOB operator is the name of an indexed column with TEXT affinity, or
the right-hand side pattern argument does not begin with a minus sign ("-") or a digit.
This constraint arises from the fact that numbers do not sort in lexicographical order. For example: 9<10 but '9'>'10'.
The built-in functions used to implement LIKE and GLOB must not have been overloaded using the sqlite3_create_function() API.
For the GLOB operator, the column must be indexed using the built-in BINARY collating sequence.
For the LIKE operator, if case_sensitive_like mode is enabled then the column must indexed using BINARY collating sequence, or if case_sensitive_like mode is disabled then the column must indexed using built-in NOCASE collating sequence.
If the ESCAPE option is used, the ESCAPE character must be ASCII, or a single-byte character in UTF-8.
I do a full text search using LIKE clause and the text can contain a '%'.
What is a good way to search for a % sign in an sqlite database?
I did try
SELECT * FROM table WHERE text_string LIKE '%[%]%'
but that doesn't work in sqlite.
From the SQLite documentation
If the optional ESCAPE clause is present, then the expression following the ESCAPE keyword must evaluate to a string consisting of a single character. This character may be used in the LIKE pattern to include literal percent or underscore characters. The escape character followed by a percent symbol (%), underscore (_), or a second instance of the escape character itself matches a literal percent symbol, underscore, or a single escape character, respectively.
We can achieve same thing with the below query
SELECT * FROM table WHERE instr(text_string, ?)>0
Here :
? => your search word
Example :
You can give text directly like
SELECT * FROM table WHERE instr(text_string, '%')>0
SELECT * FROM table WHERE instr(text_string, '98.9%')>0 etc.
Hope this helps better.
There is table column containing file names: image1.jpg, image12.png, script.php, .htaccess,...
I need to select the file extentions only. I would prefer to do that way:
SELECT DISTINCT SUBSTR(column,INSTR('.',column)+1) FROM table
but INSTR isn't supported in my version of SQLite.
Is there way to realize it without using INSTR function?
below is the query (Tested and verified)
for selecting the file extentions only. Your filename can contain any number of . charenters - still it will work
select distinct replace(column_name, rtrim(column_name,
replace(column_name, '.', '' ) ), '') from table_name;
column_name is the name of column where you have the file names(filenames can have multiple .'s
table_name is the name of your table
Try the ltrim(X, Y) function, thats what the doc says:
The ltrim(X,Y) function returns a string formed by removing any and all characters that appear in Y from the left side of X.
List all the alphabet as the second argument, something like
SELECT ltrim(column, "abcd...xyz1234567890") From T
that should remove all the characters from left up until .. If you need the extension without the dot then use SUBSTR on it. Of course this means that filenames may not contain more that one dot.
But I think it is way easier and safer to extract the extension in the code which executes the query.
I would like to know if it is possible to use [] in SQLite query as we used to in Access and other DB.
e.g. SELECT * FROM mytable WHERE fwords like '%b[e,i,a]d%'
this will retrieve all rows have fwords containing bad, bed, bid
Thanks a lot
From http://www.sqlite.org/lang_expr.html:
The LIKE operator does a pattern matching comparison. The operand to the right of the LIKE operator contains the pattern and the left hand operand contains the string to match against the pattern. A percent symbol ("%") in the LIKE pattern matches any sequence of zero or more characters in the string. An underscore ("_") in the LIKE pattern matches any single character in the string. Any other character matches itself or its lower/upper case equivalent (i.e. case-insensitive matching).
Does that help?
You can have a look at the regex section here.