Im trying to pull bunch of records from MySQL with condition whether the column value contains 0. If I convert to string and check with contains (%0%), it takes more time to execute.. Is there any short way to check on Integer column? Thank you..
You can probably run a regex on the integer column. Something like below.
SELECT fieldname FROM tablename WHERE fieldname REGEX '[0]';
About the performance, I believe that LIKE is faster than REGEX. But since your LIKE involves string conversion, this would have some difference in execution time
#SriniK You can use either POSITION() or LOCATE() in conjunction with CONVERT() to convert the column value into a string and then find if the string "0" exists within the string. Both of these functions return a positive number greater than 0 indicating the index of the substring within your string and they return a 0 if the string isn't found.
Here's how to create a simple test table to illustrate:
CREATE TABLE `testTable` (`id` INTEGER NOT NULL AUTO_INCREMENT, `someNum` INTEGER, PRIMARY KEY(`id`));
INSERT INTO `testTable` (`someNum`)
VALUES
(1),
(10),
(11),
(100),
(111),
(222),
(210);
And here are two queries illustrating both POSITION() and LOCATE():
SELECT `id`,
`someNum`,
POSITION('0' IN CONVERT(`someNum`, CHAR))
FROM `testTable`
WHERE POSITION('0' IN CONVERT(`someNum`, CHAR)) > 0
;
SELECT `id`,
`someNum`,
LOCATE('0', CONVERT(`someNum`, CHAR))
FROM `testTable`
WHERE LOCATE('0', CONVERT(`someNum`, CHAR)) > 0
;
I have mocked this up on dbfiddle here so you can get a better look at it.
If this doesn't get you what you need or if you don't understand something please leave a comment with details and I'll do what I can to help further. Good luck.
Related
I have a table which primary key is numeric and auto-incremented.
When I run a query such as:
SELECT * FROM my_table where id = '1a';
The query returns the row with the primary key set to "1".
I was not aware of this behavior, is it possible to prevent it?
I was expecting this WHERE clause to retrieve nothing since the id is "1" and not "1a". It is behaving like it was a LIKE clause.
MySQL implicitly converts a String literal to int while comparing with an int column.
You should really fix your application code (eg: PHP), and properly typecast to (int) before using them in a query. Ideally, your application should not have been inputting string values to compare against an integer field.
Now still, if you don't have control over input value, an approach can be to check if the value is numeric or not, and use it accordingly for comparison. Adapting a sargable approach from https://dba.stackexchange.com/q/89760/160363
SELECT * FROM my_table
WHERE id = CASE WHEN CONCAT('','1a'*1) = '1a' THEN '1a' ELSE NULL END;
mysql automatically converts strings to numbers, and just takes the leading characters that are digits. You could instead explicitly cast the ID to a string:
SELECT * FROM my_table where CAST(id AS CHAR) = '1a';
I have imported a CSV file that contains string values (eg.eating) and floating values (eg. 0.87) into a table in my phpMyAdmin database. After I get ride of all the string values and retain only the rows that have the decimal values, I need to convert such values from VARCHAR to DECIMAL/FLOAT so that I can perform a MAX() on this attribute.
How do I do this? Each time I try doing this through the GUI in phpMyAdmin, all my values are automatically rounded off to 0 and 1s.
Please help me!
Without Converting you can find Maximum using this query
select max(cast(stuff as decimal(5,2))) as mySum from test;
check this SQLfiddle
your demo table:
create table test (
name varchar(15),
stuff varchar(10)
);
insert into test (name, stuff) values ('one','32.43');
insert into test (name, stuff) values ('two','43.33');
insert into test (name, stuff) values ('three','23.22');
Your Query:
For SQL Server, you can use:
select max(cast(stuff as decimal(5,2))) as mySum from test;
Be aware that if you convert from VARCHAR to DECIMAL and do not specify a precicision and maximum number of digits (i.e. DECIMAL instead of DECIMAL(5,2)) MySQL will automatically round your decimals to integer values.
I think you need to try doing something like this on your MySQL if you have admin privilege on your MySQL.
ALTER TABLE tablename MODIFY columnname DECIMAL(M,D)
for the M,D variables, read this - http://dev.mysql.com/doc/refman/5.0/en/fixed-point-types.html
And MySQL should be able to automatically converting a text to a numeric. Just that the data type in MySQL might not be a decimal yet that's why you can't store any decimal.
Hope it may help someone
select convert( if( listPrice REGEXP '^[0-9]+$', listPrice, '0' ), DECIMAL(15, 3) ) from MyProduct WHERE 1
I am writing a flexible search mechanism for a customer's website. I am utilizing union clauses to query a number of different fields in the database in search of a string value entered by the user. This works fine except for one issue.
When comparing a string of a text to an integer that is currently set to zero, the match always returns true. In other words, according to MySQL, "email#example.com" is equal to 0.
I have tried utilizing the CAST and CONVERT function to turn this into a standard string to string comparison, but I can't seem to get the syntax right. My attempts either repeat the above issue or return no rows at all when some should match. I am also concerned that doing this would have an effect on performance since I am combining lots of unions.
What I really need is a strict comparison between an entered string and the value in the database, be it an integer or string.
EDIT:
Here is an example.
CREATE TABLE `test_table` (
`id` INT NOT NULL AUTO_INCREMENT ,
`email` VARCHAR(255) NOT NULL ,
`phone` BIGINT(19) NOT NULL DEFAULT '0' ,
PRIMARY KEY (`id`) )
ENGINE = MyISAM;
INSERT INTO `test_table` (`id`, `email`, `phone`) VALUES (1, 'email#example.com', 0);
SELECT * FROM test_table WHERE phone = 'email#example.com';
Execute this and the one row that has been inserted will return. My issue is that it shouldn't!
This query should fail:
SELECT * FROM test_table WHERE cast(phone as char) = 'email#example.com';
The cause of the original problem is that when comparing strings and numbers, it converts the string to a number (so you can write where phone = '123'). You need to use an explicit cast of the field to make it a string-to-string comparison, to prevent this default conversion.
Unfortunately, casting like this is likely to prevent it from using indexes. Even if the field is already char, the cast apparently prevents it from indexing.
You could also solve it during input validation: if phone is an integer, don't allow the user to provide a non-integer value in the search field.
How about replacing:
SELECT * FROM test_table WHERE phone = 'email#example.com'
with:
SELECT * FROM test_table WHERE phone = 'email#example.com' and phone <> 0
<> means different from.
This will work for you because you are using 0 in the phone column to mean there isn't a phone number (although it would be better style to use NULL for no phone number).
I'm trying to insert rows from one table to the other. In the first table, the datatype of one column is char(5), but the same column has tinyint(4) datatype in the second table. When i run the insert query, it says
Incorrect integer value: '' for column 'x' at row 258
I cannot alter or modify the datatype now as it violates some constraints. Is there a way to use cast or convert char to tinyint?
Thanks.
You probably want something like this:
INSERT INTO newtable
SELECT CASE WHEN x = '' THEN 0 ELSE x END
FROM oldtable
I'm assuming that you want blanks to turn into zeros? If not, then provide the integer value you want blanks to have.
If there are other exceptions, use more alternatives in the CASE expression.
I have a very simple rating system in my database where each rating is stored as an enum('1','-1'). To calculate the total I tried using this statement:
SELECT SUM(CONVERT(rating, SIGNED)) as value from table WHERE _id = 1
This works fine for the positive 1 but for some reason the -1 are parsed out to 2's.
Can anyone help or offer incite?
Or should I give up and just change the column to a SIGNED INT(1)?
this is what you want
select enum+0 as enum
This conversion to int in MySQL for enum is only possible:
CAST(CAST(`rating` AS CHAR) AS SIGNED) as value from table WHERE _id = 1
Yes, I'd suggest to change the type of the column. The issue becomes clear when you read the doc about enum type (which strongly recommends not to use numbers as enumeration values!) - the index of the enum item is returned, not the enum value itself.
Ok guys,
Just had a bit of a mere of a time with this one. I learned that i shouldn't use ENUMs where integers are the values. However We had years worth of data and i couldn't alter the database.
This bad boy worked (turning it into a character, then into a signed int).
CAST(CAST(`rating` AS CHAR) AS SIGNED) as value from table WHERE _id = 1
use
SELECT SUM( IF( columnname >0, CAST( columnname AS CHAR ) , NULL ) ) AS vals
FROM `tableName`
I wouldn't use enum here too, but it is still possible in this case to get what is needed
Creating table:
CREATE TABLE test (
_id INT PRIMARY KEY,
rating ENUM('1', '-1')
);
Filling table:
INSERT INTO test VALUES(1, "1"), (2, "1"), (3, "-1"), (4, "-1"), (5, "-1");
Performing math operations on enums converts them to indexes, so it is possible just to scale the result value:
SELECT
SUM(3 - rating * 2)
FROM
test;
Result: -1 which is true for the test case.