I have a stored procedure which returns multiple result sets similiar to the following:
ALTER PROCEDURE sp_XXXX
(
XXXXXX
)
AS
SET NOCOUNT ON
SELECT XXXXXXX
IF ##ROWCOUNT = 0
SELECT XXXXXXX
RETURN
I want my report to use the first result set if it has data or use the second one in case the first one is empty. Any help?
In the sproc "union all" your two result sets. If you need to tell them apart add a derived column indicating the original result set.
select 'ds1' as dataset, *
from table1
union all
select 'ds2' as dataset, *
from table2
Another try
Dump result set 1 into a temp table and only execute the second query if it's empty.
pseudo code:
select * into #tempResult
from table 1
if table1 is empty
select * from table2
Related
To get a record I normally use this kind of query:
select * from tablename where columnName = 'abc'
This query search for all abc in the table. However I want just to get only first record that has abc and don't look for other.
Please suggest me sql query for this purpose.
This will just return the first instance as it scans the table.
select * from tablename where columnName = 'abc' limit 1;
Let assume Following simple table
Col1
======
one
two
Let assume Following simple query
Select count(*) from TABLE_A where Col1 in ('one','two','three','four')
In above query it will produce following result
2
Now I want to find out what are the values in IN- condition which is not available in table_A.
How to find out that values which are not available in table?
like below result
three
four
Above queries only example. In my real time query in have 1000 values in IN-Condition.
Working Database : DB2
This is the one of the work around to achieve your expectation.
Instead of hard-coding the values in IN condition, you can move those values in to a table. If it done simply using LEFT JOIN with NULL check you can get the not matching values.
SELECT MR.Col1
FROM MatchingRecords MR -- here MatchingRecords table contains the IN condition values
LEFT JOIN Table_A TA ON TA.Col1 = MR.Col1
WHERE TA.Col1 IS NULL;
Working DEMO
If the values are to be listed in the statement string rather than stored in a table, then perhaps a revision to the syntax being used for that list of values currently being composed [apparently, from some other input than a TABLE] for the IN predicate can be effected? The following revised syntax for a list of values could be used both for the original aggregate query [shown immediately below as the first of two queries], and for the query for which the how-to-code is being asked [the second of the two queries below]:
Select count(*)
from TABLE_A
where Col1 in ( values('one'),('two'),('three'),('four') )
; -- report from above query follows:
COUNT ( * )
2
[Bgn-Edit 05-Aug-2016: adding this text and example just below]Apparently at least one DB2 variant balks at unnamed columns for the derived table, so the query just below names the column; I chose COL1, so as to match the name from the actual TABLE, but that should not be necessary. The (col1) is added to the original query that remains from the original pre-edit version; that version remains after this edit\insertion and is missing the (col1) added here:
select *
from ( values('one'),('two'),('three'),('four') ) as x (col1)
except ( select * from table_a )
; -- report from above query follows:
COL1
three
four
The following is the original query given, for which the comment below suggests a failure for an unnamed column when run on some unstated DB2 variant; I should have noted that this SQL query functions without error, on DB2 for i 7.1
[End-Edit 05-Aug-2016]
select *
from ( values('one'),('two'),('three'),('four') ) as x
except ( select * from table_a )
; -- report from above query follows:
VALUES
three
four
I have a simple query that selects one field and only one row, thus one value.
Is there any way to make it return NULL if the query results in an empty set? Instead of returning zero rows?
I think I need to use something with NOT EXISTS, THEN NULL but not certain about it.
select
(Your entire current Select statement goes here) as Alias
from
dual
dual is a built in table with a single row that can be used for purposes like this. In Oracle this is mandatory. MySQL supports it, but you can also just select a single value without specifying a table, like so:
select
(Your entire current Select statement goes here) as Alias
In either case you're selecting a single value. This means that:
If your select returns one value, that value is returned.
If your select statement returns one column, but no rows, NULL will be returned.
If your select statement returns multiple columns and/or multiple rows, this won't work and the query fails.
An easy way to do this is with aggregation:
select max(col)
from t
where <your condition here>
This always returns one row. If there is no match, it returns NULL.
Late reply but I think this is the easiest method:
SELECT
IFNULL((SELECT your query), NULL)
Use a UNION with a NOT EXISTS(original where clause)
select col1
from mytable
where <some condition>
union
select null
where not exists (
select * from mytable
where <some condition>)
You can use COALESCE for example:
SELECT COALESCE(Field1,NULL) AS Field1 FROM Table1
Edit 1:
sorry i mistake with return field as null not result set,for result set return as null use Union and Exist Function like this:
SELECT NULL AS Field1 FROM Table1 WHERE not EXISTS(SELECT Field1 FROM Table1 WHERE Field2>0)
UNION
SELECT Field1 FROM Table1 WHERE Field2>0
I need a query in which it starts off by selecting the entire table, then there would be a few more querys that would remove entries from the first query. Ive accomplished this by using several querys and then comparing the results in my application. I was wondering if I can accomplish this in a single query.
Algorithm
Select All AccountIDs from table
Select AccountIDs from table where parameter1 = true
Remove those matches from the original query result
Select AccountIDs from table where parameter2 = true
Remove those matches from the remaining query result
and so on up to N parameters.
This would need to also be compatible with both mySQL and SQLite
I think you are looking for this:
SELECT AccountID FROM the_table
LEFT JOIN (
SELECT AccountID FROM the_table
WHERE
parameter1 = true OR
... OR
parameterN = true ;
) AS not_included USING (AccountID)
WHERE not_included.AccountID IS NULL -- only items with no match in the "not_included" sub-query
The not_included subquery returns all items for which any parameter is set to TRUE. You actually want to exclude these records from your final result set.
Then LEFT-JOIN the_table (i.e. all items) to this sub-result. The WHERE...IS NULL clause excludes items present in the_table but not present in not_included.
Therefore only items which you do not want to exclude remain in the final result set.
The most direct way to implement your algorithm is to use a compound SELECT statement:
SELECT AccountID FROM MyTable
EXCEPT
SELECT AccountID FROM MyTable WHERE parameter1 = 1
EXCEPT
SELECT AccountID FROM MyTable WHERE parameter2 = 1
However, this is also possible with a single WHERE expression:
SELECT AccountID
FROM MyTable
WHERE NOT (parameter1 = 1 OR
parameter2 = 1 OR
...)
My query is like this
select 5 from mytable_name;
Then the output is like column name 5 and the value is 5 printing as many max number of rows exists in that table.
Can anybody tell the reason why this query is working like this?
Can anybody tell the reason why this query is working like this?
You are selecting a string literal value '5' for each row in your table:
select 5 from mytable_name;
And this works fine. Because in the SELECT statement you can select:
Column reference,
Literal value like in your case.
Function.
value expression.
Select expression.
As defined by the standard SQL1:
Update:
However, If you have a column with a name is a number like in your case, you have to escape it in order to select the values in it like so:
SELECT `143` FROM Table1;
This will select all the rows in the column 143.
But, this:
SELECT 143 FROM Table1;
Will select the string literal 143 for each row found in the table.
Note that: If possible, try not to name these columns this way, it is recommended and a best practice, not to do this.
SQL Fiddle Demo
Update 2:
Note that, if you select 143 or '143', or even "143" this will select the literal value 143 not the column date. The following are the same:
SELECT 143 FROM Table1;
SELECT '143' FROM Table1;
SELECT "143" FROM Table1;
All these SELECTs won't select the data in the column, They will select the literal value 143 not the column data. See this demo:
Demo
You have to escape the column name with the two:
``
Like this:
SELECT `143` FROM table1;
Not:
SELECT '143' FROM table1'
Like what I did here:
The right Demo
1Image From: SQL Queries for Mere Mortals
from mytable
will select all rows from your table if there is no where condition that shrinks that result. and
select 5
will select the constant number 5 for every record. If you use a column name in the select part then that value will be selected for every record.
The DB engine will name the result 5 because it automatically generates a column name and 5 is the logical name for that.
You want 'SELECT * FROM mytable_name LIMIT 0,5' perhaps?
Since you don't have anything in your where clause, it is selecting all the rows from your table. The fact that you don't select any of the columns is irrelevant - you'll still get a result for each row in the table.
With the command select 5 ... you are viewing a fixed value. Same thing you run the following command: select "test", you will be displaying a fixed string.
Using ... from mytable_name you're looking for all record of this table.
With this we can conclude that for each record in the table mytable_name shows you the fixed value "5".