Why specifically '%' used in SQL for searching something with LIKE Query. Eg: If i want to search all the persons with name starting with word 's' why i have to write "LIKE 's%'" but not just write "LIKE 's'"
A wildcard character(%) is used to substitute one or more characters in a string. This is used to denote and display all other character which comes after the selected string in sql query. Because of that, we are using like letter% in sql query.
Related
Using SQL I would like to know if its possible to do the following:
If I have a variable that the user inputs mutiple strings into seperated by a comma for example ('aa','bbb','c','dfd'), is it possible using LIKE with a wilcard at the end of each string in stead of having the user to enter each variations in multiple macros.
So say if user was looking for employee numbers that start with ('F','E','C') is it possible without using OR statements is the question I guess am asking?
It would be similar to that of an array I guess
No, LIKE is its own operator and therefore needs separated by an OR.
You might prefer ILIKE to LIKE, as it is a case-insensitive comparison.
You can also try to use REGEXP_LIKE, which is similar to what you want, except you'll have to use regex expressions instead of 'FEC%'
That depends on your SQL dialect; I don't know Impala at all, but other SQL engines have support for regular expressions in string matches, so that you can build a query string like
SELECT fld FROM tbl WHERE fld REGEXP '^[FEC].*$';
No matter what you do, you will need to build a query from your user's input. Passing through user input unprocessed into your SQL processor is a big "nope" anyways, from a "don't accidentally delete a table" point of view:
I have a query which is supposed to find matching rows ignoring case and special characters that may be present both in the query and the corresponding column. For that I use REGEXP_REPLACE like this:
SELECT *
FROM Order
WHERE REGEXP_REPLACE(reference, '[^a-zA-Z0-9äöüÄÖÜ]', '') LIKE %:search%
where search is the name of the parameter I want to use. That works, but doesn't yet sanitize the search parameter from unwanted special characters.
What I would like to do is something like the following, i.e. having the REGEXP_REPLACE on the right side as well:
SELECT *
FROM Order
WHERE REGEXP_REPLACE(reference, '[^a-zA-Z0-9äöüÄÖÜ]', '') LIKE %REGEXP_REPLACE(:search, '[^a-zA-Z0-9äöüÄÖÜ]', '')%
However that doesn't work and I get the following error:
42000][1064] You have an error in your SQL syntax; check the manual that corresponds to your MariaDB server version for the right syntax to use near '%REGEXP_REPLACE(
Is it not possible to use a function on the parameter or as part of a LIKE statement? Are there any workarounds?
It looks like you want to create a string starting and ending with '%' to use in your LIKE operator. To do that in MySQL's dialect of SQL you need to do your string manipulation explicitly using the built-in string manipulation functions.
You can use those functions anywhere your query needs a text string.
Try using CONCAT in an expression like this to generate that string. You'll be able to use it on the right side of your LIKE.
CONCAT('%', REGEXP_REPLACE(:search, '[^a-zA-Z0-9äöüÄÖÜ]', ''), '%')
I hope you don't want your query to be fast. It will be slow. It must examine every value of Order.reference in your table. It's slow because
it's not sargable due to WHERE f(column) LIKE whatever, and
column LIKE '%something%' requires looking at every value of column, rather than random-acccessing a BTREE index.
If you build a database to scale up, you design it so your queries can be sargeable. Sargability here might look like
WHERE cleaned_up_reference
LIKE CONCAT(REGEXP_REPLACE(:search, '[^a-zA-Z0-9äöüÄÖÜ]', ''), '%')
without the leading % on the right, and without evaluating any function on the column or columns being searched.
You can try this:
SELECT * FROM Order a
WHERE REGEXP_REPLACE(a.reference, '[^a-zA-Z0-9äöüÄÖÜ]', '') LIKE '%:search%'
I have been searching for a way of using Django ORM to use the SQL underscore wildcard, and do something equivalent to this:
SELECT * FROM table
WHERE field LIKE 'abc_wxyz'
Currently, I am doing:
field_like = 'abc_wxyz'
result = MyClass.objects.extra(where=["field LIKE " + field_like])
I already tried with contains() and icontains(), but that's not what I need, since what it does is adding parenthesis to the query:
SELECT * FROM table
WHERE field LIKE '%abc/_wxyz%'
Thanks!
You can use __regex lookup to build more complex lookup expressions than __contains, __startswith or __endswith (can add "i" character to beginning of each of these to make lookups case insensitive, like icontains). In your case, I think
MyClass.objects.filter(field__regex=r'^abc.wxyz$')
Would do what you are trying to do.
You can use the field__contains attribute.
for example:
MyClass.objects.filter(field__contains='abc_wxyz')
This is equivalent to:
SELECT * FROM MyClass WHERE field LIKE 'abc_wxyz'
Lord Elron's answer is incorrect. Django escapes all developer supplied wildcard characters to the LIKE-type lookups. The statement is equivalent to
SELECT * FROM MyClass WHERE field LIKE '%abc/_wxyz%'
(as the OP discovered) and the underscore has no effect.
See Escaping percent signs and underscores in LIKE statements
The field lookups that equate to LIKE SQL statements (iexact, contains, icontains, startswith, istartswith, endswith and iendswith) will automatically escape the two special characters used in LIKE statements – the percent sign and the underscore.
I'm currently using Oracle SQL developer and am trying to write a query that will allow me to search for all fields that resemble a certain value but always differ from it.
SELECT last_name FROM employees WHERE last_name LIKE 'Do[^e]%';
So the result that I'm after would be: Give me all last names that start with 'Do' but are not 'Doe'.
I got the square brackets method from a general SQL basics book so I assume any SQL database should be able to run it.
This is my first post and I'd be happy to clarify if my question wasn't clear enough.
In Oracle's LIKE no regular expressions can be used. But you can use REGEXP_LIKE.
SELECT * FROM EMPLOYEES WHERE REGEXP_LIKE (Name, '^Do[^e]');
The ^ at the beginning of the pattern anchors it to the beginning of the compared string. In other words the string must start with the pattern to match. And there is no wildcard needed at the end, as there is no anchor for the end of the string (which would be $). And you seem to already know the meaning of [^e].
How am I going to use BETWEEN Operator with Text Value or what is the right syntax when you will select all products with a ProductName for example ending with any of the letter BETWEEN 'C' and 'M'?
Most SQL dialects provide the RIGHT() function. This allows you to do:
WHERE RIGHT(TextValue, 1) BETWEEN 'C' AND 'M'
If your database doesn't have this function, you can do something similar with the built-in functions. Also, the exact comparison might depend on the collation of the column/table/database/server. Sometimes comparisons are independent of case and sometimes they are dependent on case.
In case you are interested in an alternative method (which does work with the w3schools SQL editor), you can also use the LIKE operator:
WHERE ProductName LIKE '%[c-m]'
This will get you all Product Names ending on any character between C and M.
(It does work with the w3schools SQL Editor.)
In this case, the LIKE operator is using two wildcard characters:
1.%
Any string of zero or more characters.
2.[c-m]
Any single character within the specified range ([a-f]) or set
([abcdef]).
You can find more information about the LIKE operator here:
https://msdn.microsoft.com/en-us/library/ms179859.aspx