I have an sql query that could potentially return null values, in the event of this I want the query to return '0'. Here is the query
SELECT (select count(goal) from fixtures where goal='1' and fixture='$fixture') as goalCountHome
from fixtures where fixture='$fixture'LIMIT 1
Any help much appreciated!
In MySql use IFNULL() function. For MsSql use ISNULL() function.
If you are using MySql, IFNULL(<column_name>, 0) should do.
This query:
SELECT (select count(goal) from fixtures where goal='1' and fixture='$fixture') as goalCountHome
FROM fixtures
WHERE fixture = '$fixture'
LIMIT 1
cannot return NULL values. The subquery is an aggregation query with no GROUP BY, so it always returns one row. That row will contain a result from COUNT(). COUNT() itself can never return a NULL value. If there are no rows, then the value will be zero.
The outer query might return no rows but that is different from NULL values.
Of course, this query is way overcomplicated, and should simply be:
SELECT COUNT(*) as goalCountHome
FROM fixtures
WHERE fixture = ? AND -- pass this in as a parameter
goal = 1 ; -- it looks like a number so I assume it is
Note that you should be passing parameters in using proper parameters rather than munging query strings.
if you need all the rows and not the rows where goal is not null you could use count(*)
select count(*)
from fixtures
where goal=1
and fixture='$fixture'
count(goal) return the number of rows where goal is not null
count(*) return the total number rows selected
otherwise in general when you need not null values in mysql you can ifnull(your_column, value) or coalesce(your_column, value)
based on you comment seems you need sum(goal)
select sum(ifnull(goal,0))
from fixtures
where goal=1
and fixture='$fixture'
Related
I want to obtain unread messages count from MySQL database using SELECT SUM operator.
So, my SQL is:
SELECT sum(status_field = 'new') unreadMessagesCount
FROM messages
WHERE 'author_uid' = 'authorUID'
And it returns NULL. Why?
I have items in database and I can select it by (SELECT * FROM messages)
It returns NULL because you are comparing strings, not columns with:
WHERE 'author_uid' = 'authorUID'
And these two strings are not equal. So, all rows are filtered out. The NULL value is because you have an aggregation query. SUM() returns NULL when there are no rows in such a query.
I'm not sure what you intend. Perhaps:
WHERE author_uid = 'authorUID'
However, 'authorUID' seems like a strange value for a uid. You need to put an appropriate value there. If it is a string, enclose it in single quotes. If it is a number, do not use single quotes.
I want to return a select query with zero result. When I type this query:
Select NULL .... from ....
It returns NULL value as a result. But I want to return zero result instead of NULL. So, how to do that? I use coalesce but if I have value, it doesn't return zero. So, what should select query use to return zero value? I use MYSQL.
If you want to add column to existing columns you can use the below instead.
Select *,0 as ZeroColumn from ....
I can't imagine why you want to do this, but if you do it's quite simple. SELECT 0 will return zero once. SELECT 0 FROM MyTable will return zero once for each record in MyTable.
I currently am using this query to select some data:
SELECT DISTINCT a.code AS code, name, max(scen.Is3D) AS Is3D FROM locations LEFT JOIN .... The scen table has columns Is3D and Date. I only want to select the max of items where the date IS NOT NULL. I tried max(scen.Is3D WHERE scen.Date IS NOT NULL), but that didn't work. I cannot change anything after the FROM in my query, so I need that filtering to be done in the MAX, if possible. I am using MySQL 5.7.
You can use:
MAX(CASE WHEN scen.date IS NOT NULL THEN scen.Is3D END) AS Is3D
The CASE expression returns NULL when none of the WHEN conditions is met, but MAX() ignores null values, so this will just return the max of the Is3D columns in the selected rows.
So if we can't change anything after the FROM, then we cannot get a perfect solution here. Since you are SELECTing out the NULL values. One thing that we can try if we can only modify the final output is this.
SELECT MAX(ISNULL(scen.Date,0))...
This will replace all the NULLs with 0, but it would help to know exactly what you are trying to do. Why are you so convinced that the query itself cannot be modified in any way?
The other solution would be to put the whole query in another wrapper.
That would look like:
SELECT *
FROM (
[your whole query here]
) AS inner
WHERE inner.Date IS NOT NULL
This query will return you 0 records if no records exist in TableA:
Select strA, strB, intC, floatD, from tableA
However, this query returns 1 records with all columns as Null.
Select strA, strB, intC, floatD, sum(intC+intD) as sumE,
from tableA
So, to fix it, I did:
Select strA, strB, intC, floatD, sum(intC+intD) as sumE,
from tableA
having sumE is not null
I was wondering if there is a better way to do the same thing. Any in-built MySQL function that can do the same thing?
That's because you don't have a GROUP BY. You're asking MySQL to get you the SUM of intC + intD for the entire table, so it's going to give you a result no matter what. It has to put in something for strA, strB, etc. so it puts in NULL values.
For example, just do SELECT SUM(intA) FROM tableA and you'll get NULL.
I have the following SQL statement:
SELECT name, SUM(growth) AS sum_buy_price, SUM(recovery) AS sum_msrp, SUM(growth)+SUM(recovery) AS total
FROM orders
WHERE id = ?
GROUP BY name
My data is coming from a CSV file that I have no control over and either 'growth' or 'recovery' can be NULL in the data, but not at the same time. I need to use ISNULL to convert the possible NULL values to zero in order for the SUM to work correctly, but I'm unsure of how/where to add the ISNULL since the SELECT is indexing another record (name).
ISNULL returns whether the argument passed is null (i.e., it is analogous to true or false). I suppose, what you need is IFNULL:
SELECT
name,
SUM(IFNULL(growth, 0)) AS sum_buy_price,
SUM(IFNULL(recovery, 0)) AS sum_msrp,
SUM(IFNULL(growth, 0))+SUM(IFNULL(recovery,0)) AS total
FROM
orders
WHERE
id = ?
GROUP BY
name
The SUM() function ignores NULL values, so you don't need to change a NULL to a 0 in order for it to work properly.
If however, all values that you're aggregating are NULL and you want to return a 0 instead of NULL you can use IFNULL() or the more common COALESCE() to show 0 as the sum instead of NULL:
SELECT COALESCE(SUM(growth),0)
ISNULL() is a valid SQL Server function, IFNULL() is the equivalent in MySQL, but all major databases make use of COALESCE() which returns the first non-NULL value in a set, ie: COALESCE(NULL,NULL,5) would return 5.
This should work for you:
SELECT name, SUM(ISNULL(growth, 0)) AS sum_buy_price,
SUM(ISNULL(recovery, 0)) AS sum_msrp,
SUM(ISNULL(growth, 0))+SUM(ISNULL(recovery,0)) AS total
FROM orders
WHERE id = ?
GROUP BY name