MySQL IF NOT NULL, then display 1, else display 0
I'm working with a little display complication here. I'm sure there's an IF/ELSE capability I'm just overlooking.
I have 2 tables I'm querying (customers, addresses). The first has the main record, but the second may or may not have a record to LEFT JOIN to.
I want to display a zero if there is no record in the addresses table. And I want to only display 1, if a record exists.
What I've attempted so far:
SELECT c.name, COALESCE(a.addressid,0) AS addressexists FROM customers c LEFT JOIN addresses a ON c.customerid = a.customerid WHERE customerid = 123
This first example does not do it. But I may be utilizing COALESCE wrong.
How can I display a 0, if null, and a 1, if something exists?
COALESCE(a.addressid,0) AS addressexists, use
CASE WHEN a.addressid IS NOT NULL THEN 1 ELSE 0 END AS addressexists
or the simpler:
(a.addressid IS NOT NULL) AS addressexists
This works because
TRUE is displayed as
1 in MySQL and
MySQL IFNULL, MySQL IFNULL function is one of the MySQL control flow functions that accepts The IFNULL function returns expression_1 if expression_1 is not NULL ; otherwise, it returns expression_2 . If you want to return a value based on TRUE or FALSE condition other than NULL IFNULL(1,0) returns 1 because 1 is not NULL . The following SQL statement will display the number of books purchase which publish by the language English and Non-English in a row. Code: SELECT SUM(IF(pub_lang = 'English',1,0)) AS English, SUM(IF(pub_lang . > 'English',1,0)) AS "Non English" FROM purchase;
SELECT c.name, IF(a.addressid IS NULL,0,1) AS addressexists FROM customers c LEFT JOIN addresses a ON c.customerid = a.customerid WHERE customerid = 123
Careful if you're coming from C/C++ and expecting this to work:
select if(name, 1, 0) ..
Even if 'name' is not NULL, unlike in C, a false-condition still triggers and the above statement returns 0. Thus, you have to remember to explicitly check for NULL or empty string:
select if(name is null or name = '', 0, 1)
PS Eugen's example up above is correct, but I wanted to clarify this nuance as it caught me by surprise.
MySQL IF() function, mysql> SELECT IF((SELECT CASE WHEN 1>0 THEN 'true' ELSE the pub_lang column displays NULL values, which is not meaningful for� I've been tasked with coming up with a means of translating the following data: FROM dates saved in [OccuredAtUtc] that look like this: 2016-11-19 10:35:13.5790000 2016-12-21 12:16:58.5080000 20
SELECT c.name, CASE WHEN a.addressid IS NULL THEN 0 ELSE 1 END AS addressexists FROM customers c LEFT JOIN addresses a ON c.customerid = a.customerid WHERE customerid = 123
SQL ISNULL(), NVL(), IFNULL() and COALESCE , In simple terms, NULL is simply a place holder for data that does not exist. When 1, Janet Jones, Female, 21-07-1980, First Street Plot No 4, Private Bag, 0759 253 542 It returns true if the supplied value is not NULL and false if the supplied value is null. The query result is 0 which means FALSE. SELECT TOP 1 WITH TIES tbl1.* FROM (SELECT CASE WHEN S.Id IS NOT NULL AND S.Status = 1 AND (S.WebUserId = @WebUserId OR S.AllowUploads = 1) THEN 1 ELSE 0 AS [Value] FROM Sites S WHERE S.Id = @SiteId) as tbl1 ORDER BY tbl1.[Value]
Another method without WHERE, try this..
Will select both Empty and NULL values
SELECT ISNULL(NULLIF(fieldname,'')) FROM tablename
It will set null if it is an empty string, then be true on that also.
MySQL IS NULL & IS NOT NULL Tutorial with EXAMPLES, In MySQL, sometimes you don't want NULL values to be returned as CASE WHEN TaskCode IS NOT NULL THEN TaskCode ELSE 'N/A'� Hi All, I am having problems with the following SELECT CASE statement when trying to handle NULL values. In the following select SELECT st3.description , CASE st3.description
4 Ways to Replace NULL with a Different Value in MySQL , If expr1 is not NULL, IFNULL() returns expr1 ; otherwise it returns expr2 . IFNULL () returns a numeric or string value, depending on the context in which it is used. In this article, we will talk about IF and Else control structure which will work inside the procedure and how an if function, which will even work in the simple query too, explained below. We can use If and else control structure in two ways in MySQL. 1. IF and ELSE control structure. If and Else control structure works only inside of a procedure.
IFNULL, To test for NULL , use the IS NULL and IS NOT NULL operators, as shown here: mysql> SELECT 1 IS NULL In MySQL, 0 or NULL means false and anything else means true. The default truth value from a boolean operation is 1 . This special� If a given search_condition evaluates to true, the corresponding THEN or ELSEIF clause statement_list executes. If no search_condition matches, the ELSE clause statement_list executes. Each statement_list consists of one or more SQL statements; an empty statement_list is not permitted. An IF
126.96.36.199 Working with NULL Values, The SQL predicate is [not] null tests whether the result of an expression is null or not. differently: Db2, MySQL and MariaDB act in the spirit of the SQL standard and return null . ORDER BY CASE WHEN c IS NULL THEN 0 ELSE 1 END , c. Suggest to check for return row from sql query, if zero, create a datatable dynamically with the columns identical to the expected return columns of the sql query ,i.e. id, description, price, then add a row with the data that you decide, i.e. 0, 'no record', 0. Then bind it to the gridview. See example: 1. show-header-and-footer-rows-in-empty-row
- possible duplicate of Conditional NOT NULL case SQL
- Also useful: select IFNULL(fieldname, "1") from tablename;