In Postgre, why does
select abc from (select 1) as abc
produces:
(1)
and
select * from (select 1) as abc
produces:
1
That's really strange to me. Is that the case with MySQL, Oracle, etc?
I spent hours figuring out why my conditions were failing...
The rows returned by your queries have different type: the first one is ROW(INT), while the second one is INT.
MySQL and others lack this feature.
In your first query, you are selecting a whole ROW as a single column. This query
SELECT abc FROM (SELECT 1, 2) abc
will produce (1, 2), which is a single column too and has type ROW.
To select the INT value, use:
SELECT abc.col
FROM (
SELECT 1 AS col
) abc
Related
Is it possible to build a select query that sums up value of a column and also get the fields from the column of the same table, and an example please . I am new to DB2 and still learning.
I tried using the below,
SELECT SUM(Column containing numbers)
,Column 2
FROM Table
but this gives me a SQL return code of -122
It's possible with the SUM olap function.
SELECT
SUM(C1) OVER () AS C1_SUM
, C2
FROM
(
SELECT 1, 'A' FROM SYSIBM.SYSDUMMY1
UNION ALL SELECT 2, 'B' FROM SYSIBM.SYSDUMMY1
) T (C1, C2)
C1_SUM
C2
3
B
3
A
fiddle
How to use substring of a column from one table as like to a column in some other table ? For example I tried using the below query however its give me error.
SELECT LABORCODE FROM labor WHERE worklocation like (SELECT substr(location,1,4) FROM person)+ '%';
If Substring of location from PERSON table returns 1234 then the final output should appear as below,
LABORCODE LOCATION
A 1234
B 12345
C 123456
Basically the substr (location) from PERSON table should be used as a input to worklocation field in LABOR table with LIKE function.
|| instead of +:
SELECT LABORCODE
FROM labor
WHERE worklocation like
(
SELECT substr(location,1,4)
FROM person
FETCH FIRST 1 ROW ONLY
) || '%';
I've added the FETCH FIRST 1 ROW ONLY clause just in case, since the subselect must not return more than 1 row.
If your subselect returns multiple rows, then you may rewrite your query like this:
SELECT LABORCODE
FROM labor
WHERE EXISTS
(
SELECT 1
FROM person
WHERE labor.worklocation LIKE substr(person.location, 1, 4) || '%'
);
I'm trying to create a table with the following columns:
I want to use a with recursive table to do this. The following code however is giving the following error:
'ERROR: column "b" does not exist'
WITH recursive numbers AS
(
SELECT 1,2,4 AS a, b, c
UNION ALL
SELECT a+1, b+1, c+1
FROM Numbers
WHERE a + 1 <= 10
)
SELECT * FROM numbers;
I'm stuck because when I just include one column this works perfectly. Why is there an error for multiple columns?
This appears to be a simple syntax issue: You are aliasing the columns incorrectly. (SELECT 1,2,4 AS a, b, c) is incorrect. Your attempt has 5 columns: 1,2,a,b,c
Break it down to just: Select 1,2,4 as a,b,c and you see the error but Select 1 a,2 b,4 c works fine.
b is unknown in the base select because it is being interpreted as a field name; yet no table exists having that field. Additionally the union would fail as you have 5 fields in the base and 3 in the recursive union.
DEMO: http://rextester.com/IUWJ67486
One can define the columns outside the select making it easier to manage or change names.
WITH recursive numbers (a,b,c) AS
(
SELECT 1,2,4
UNION ALL
SELECT a+1, b+1, c+1
FROM Numbers
WHERE a + 1 <= 10
)
SELECT * FROM numbers;
or this approach which aliases the fields internally so the 1st select column's names would be used. (a,b,c) vs somereallylongalias... in union query. It should be noted that not only the name of the column originates from the 1st query in the unioned sets; but also the datatype for the column; which, must match between the two queries.
WITH recursive numbers AS
(
SELECT 1 as a ,2 as b,4 as c
UNION ALL
SELECT a+1 someReallyLongAlias
, b+1 someReallyLongAliasAgain
, c+1 someReallyLongAliasYetAgain
FROM Numbers
WHERE a<5
)
SELECT * FROM numbers;
Lastly, If you truly want to stop at 5 then the where clause should be WHERE a < 5. The image depicts this whereas the query does not; so not sure what your end game is here.
Currently I've a query as follows:
-- Query 1
SELECT
acc_code, acc_name, alias, LAmt, coalesce(LAmt,0) AS amt
FROM
(SELECT
acc_code, acc_name, alias,
(SELECT
(SUM(cr_amt)-SUM(dr_amt))
FROM
ledger_mcg l
WHERE
(l.acc_code LIKE a.acc_code + '.%' OR l.acc_code=a.acc_code)
AND
fy_id=1
AND
posted_date BETWEEN '2010-01-01' AND '2011-06-02') AS LAmt
FROM
acc_head_mcg AS a
WHERE
(acc_type='4')) AS T1
WHERE
coalesce(LAmt,0)<>0
Query 2 is same as Query 1 except that acc_type = '5' in Query 2. Query 2 always returns a resultset with a single row. Now, I need the union of the two queries i.e
Query 1
UNION
Query 2
only when the amt returned by Query 2 is less than 0. Else, I don't need a union but only the resulset from Query 1.
The best way I can think of is to create a parameterised scalar function. How best can I do this?
You could store the result of the first query into a temporary table, then, if the table wasn't empty, execute the other query.
IF OBJECT_ID('tempdb..#MultipleQueriesResults') IS NOT NULL
DROP TABLE #MultipleQueriesResults;
SELECT
acc_code, acc_name, alias, LAmt, coalesce(LAmt,0) AS amt
INTO #MultipleQueriesResults
FROM
(SELECT
acc_code, acc_name, alias,
(SELECT
(SUM(cr_amt)-SUM(dr_amt))
FROM
ledger_mcg l
WHERE
(l.acc_code LIKE a.acc_code + '.%' OR l.acc_code=a.acc_code)
AND
fy_id=1
AND
posted_date BETWEEN '2010-01-01' AND '2011-06-02') AS LAmt
FROM
acc_head_mcg AS a
WHERE
(acc_type='4')) AS T1
WHERE
coalesce(LAmt,0)<>0;
IF NOT EXISTS (SELECT * FROM #MultipleQueriesResults)
… /* run Query 2 */
i am trying to run an export on a system that only allows t-sql. i know enough of php to make a foreach loop, but i don't know enough of t-sql to generate multiple rows for a given quantity.
i need a result to make a list of items with "1 of 4" like data included in the result
given a table like
orderid, product, quantity
1000,ball,3
1001,bike,4
1002,hat,2
how do i get a select query result like:
orderid, item_num, total_items,
product
1000,1,3,ball
1000,2,3,ball
1000,3,3,ball
1001,1,4,bike
1001,2,4,bike
1001,3,4,bike
1001,4,4,bike
1002,1,2,hat
1002,2,2,hat
You can do this with the aid of an auxiliary numbers table.
;WITH T(orderid, product, quantity) AS
(
select 1000,'ball',3 union all
select 1001,'bike',4 union all
select 1002,'hat',2
)
SELECT orderid, number as item_num, quantity as total_items, product
FROM T
JOIN master..spt_values on number> 0 and number <= quantity
where type='P'
NB: The code above uses the master..spt_values table - this is just for demo purposes I suggest you create your own tally table using one of the techniques here.
If you are on SQL Server 2005 or later version, then you can try a recursive CTE instead of a tally table.
;WITH CTE AS
(
SELECT orderid, 1 item_num, product, quantity
FROM YourTable
UNION ALL
SELECT orderid, item_num+1, product, quantity
FROM CTE
WHERE item_num < quantity
)
SELECT *
FROM CTE
OPTION (MAXRECURSION 0)
I'm not on a computer with a database engine where I can test this, so let me know how it goes.
Well, IF you know the maximum value for the # of products for any product (and it's not too big, say 4), you can:
Create a helper table called Nums containing 1 integer column n, with rows containing 1,2,3,4
Run
SELECT * from Your_table, Nums
WHERE Nums.n <= Your_table.quantity