I have a PostgreSQL function similar to this:
CREATE OR REPLACE FUNCTION dbo.MyTestFunction(
_ID INT
)
RETURNS dbo.MyTable AS
$$
SELECT *,
(SELECT Name FROM dbo.MySecondTable WHERE RecordID = PersonID)
FROM dbo.MyTable
WHERE PersonID = _ID
$$ LANGUAGE SQL STABLE;
I would really like to NOT have to replace the RETURNS dbo.MyTable AS with something like:
RETURNS TABLE(
col1 INT,
col2 TEXT,
col3 BOOLEAN,
col4 TEXT
) AS
and list out all the columns of MyTable and Name of MySecondTable. Is this something that can be done? Thanks.
--EDIT--
To clarify I have to return ALL columns in MyTable and 1 column from MySecondTable. If MyTable has >15 columns, I don't want to have to list out all the columns in a RETURNS TABLE (col1.. coln).
You just list the columns that you want returned in the SELECT portion of your SQL statement:
SELECT t1.column1, t1.column2,
(SELECT Name FROM dbo.MySecondTable WHERE RecordID = PersonID)
FROM dbo.MyTable t1
WHERE PersonID = _ID
Now you'll just get column1, column3, and name returned
Furthermore, you'll probably find better performance using a LEFT OUTER JOIN in your FROM portion of the SQL statement as opposed to the correlated subquery you have now:
SELECT t1.column1, t1.column2, t2.Name
FROM dbo.MyTable t1
LEFT OUTER JOIN dbo.MySecondTable t2 ON
t2.RecordID = t1.PersonID
WHERE PersonID = _ID
Took a bit of a guess on where RecordID and PersonID were coming from, but that's the general idea.
Related
I have two tables that am using union to combine the result-set of them my problem here is Each SELECT statement within UNION must have the same number of columns and data types, I don't have the same number of columns so am creating null columns
select
d.deal_id as order_id,
EXISTS(select * from table1 c where d.user_id = c.user_id) as IsUser, --this returns boolean value
from table 1 c
union
select
cast(o.id as varchar) as order_id,
coalesce('No_user'::text,'0'::text) as IsUser, --i get an error :UNION types boolean and character varying cannot be matched
from table2 o
how can I create a null column in table2 that matches the boolean data type of the table1
how can I create a null column in table2 that matches the boolean data type of the table1
By putting NULL into the SELECT list of the second query.
Generally (in SQL) the datatype for the column is dictated by the first query in the union set and other queries must match. You don't need column aliases for subsequent queries either, but they may help make a query more readable:
select
d.deal_id as order_id,
EXISTS(select * from table1 c where d.user_id = c.user_id) as IsUser, --this returns boolean value
from table 1 c
union
select
cast(o.id as varchar) as order_id,
null --IsUser
from table2 o
If you have a case where the type of the column in the first query is different to what you want in the output, you cast the first column:
select 1::boolean as boolcol
UNION
select true
This will ensure that the column is boolean, rather than giving a "integer and bool cannot be matched". Remember also that, should you need to, NULL can be cast to a type, e.g. select null::boolean as bolcol
The Customer, Musician, and Staff tables in my database include a column called FirstName. The query below returns the most occurring FirstName in those three tables and returns multiple FirstNames if more than one FirstNames occurs the same amount of times.
WITH AllFirstNames AS (
SELECT FirstName
FROM Customer
UNION ALL
SELECT FirstName
FROM Musician
UNION ALL
SELECT FirstName
FROM Staff
), FirstNameOccurrences AS (
SELECT FirstName,
COUNT(*) AS Occurrences
FROM AllFirstNames
GROUP BY FirstName
)
SELECT FirstName AS MostOccurringFirstNames
FROM AllFirstNames
WHERE FirstName IN (
SELECT FirstName
FROM FirstNameOccurrences
WHERE Occurrences IN (
SELECT MAX(Occurrences)
FROM FirstNameOccurrences
)
)
GROUP BY MostOccurringFirstNames;
This only works if the tables which include the FirstName column are specified in the query which returns the temporary AllFirstNames table. If a new table with a FirstName column is added to the database, then this query will have to be updated manually. What do I need to do to the query which returns the temporary AllFirstNames table for it to dynamically UNION ALL FirstName columns from all tables which include a FirstName column? I understand that this will only work if the same naming convention is used throughout the databases lifetime.
The query below lists all the tables that include a FirstName column, but I don't know where to go from there.
SELECT table_name
FROM information_schema.columns
WHERE column_name = 'FirstName';
This does sound like a strange database design, but you can do that by creating a function that iterates over all tables.
The following function counts the distinct values per table.
create or replace function count_names()
returns table(tablename text, firstname text, occurrences bigint)
as
$$
declare
l_row record;
begin
for l_row in select distinct table_schema, table_name, column_name
from information_schema.columns
where table_schema = 'public'
and column_name = 'firstname'
loop
return query execute
format('select %L as tablename, cast(%I as text), count(*) occurrences from %I.%I group by %I',
l_row.table_name, l_row.column_name, l_row.table_schema, l_row.table_name, l_row.column_name);
end loop;
end;
$$
language plpgsql;
The above runs a count()/group by for every table that has a column named firstname in the schema public. The result can then be summed. I included the source table name in the result for debugging purposes, but it's not really needed.
With that function you can do something like this:
select firstname, sum(occurrences) num_names
from count_names()
order by num_names desc
limit 10;
Dynamic SQL is best created using the format() function to properly deal with identifiers. The column and table names you used in your question suggests you created them using the dreaded double quotes ("FirstName" is something different than FirstName) - you should really rethink that. Avoid those dreaded double quotes in SQL
table1
id col1 col2 col3...
table2
col_id col_name
3432 col1
5342 col2
6756 col3
Now I want to generate table 3 like this:
id col_name col_value col_id
Please note that col1, col2,col3... are not in order. Therefore I have to query table2 to obtain col_id ( I think pivot does not work here)
How can I do it in SQL?
It appears that you want a select like this:
SELECT t2.id,
CASE
WHEN t2.col_name='col1' THEN t1.col1
WHEN t2.col_name='col2' THEN t1.col2
WHEN t2.col_name='col2' THEN t1.col2
-- ... more columns
ELSE NULL
END
FROM table2 t2 LEFT JOIN table2 t1 ON t2.col_id = t1.id
You could also create a function, though this will be slower in practice:
CREATE OR REPLACE FUNCTION table1_col(id integer, name text) RETURNS text as $$
DECLARE
col_val text;
BEGIN
EXECUTE format('SELECT %s FROM table1 WHERE id=$1', name)
INTO col_val
USING id;
RETURN col_val;
END;
$$ LANGUAGE plpgsql;
SELECT table1_col(col_id,col_name) FROM table2;
I would like to create a function that returns a column of a table as an integer array.
In other words, how can I transfrom the result of SELECT id FROM mytable to integer[] ?
You can do:
SELECT ARRAY(SELECT id FROM mytable)
Or:
SELECT array_agg(id) FROM mytable
Bit rusty in sql
I have a situation where I need to insert a field "#Amount" into a temp table.If #amount from tableA is null or 0 get it from tableB
This is a simplified example of what I am doing.This must be done within a select statement when inserting into #CustomerTable
Do I need a case when statement?
DECLARE #Amount DECIMAL(18,4)
SELECT #Amount=Amount
FROM TableA
INSERT #CustomerTable(id,Name,Amount)
SELECT 1,CustomerName,--if Amount is null or 0 get it from TableB else Get it from Table A.
FROM TableB
Since you're using 2008 I'd twist the new NULLIF() function with the ISNULL() function and use a subquery:
insert #CustomTable (id, name, amount)
select
1,
CustomerName,
ISNULL(NULLIF(TableA.Amount,0),(select Amount from TableB where TableB.ID = TableA.ID))
from
TableA
INSERT #CustomerTable(id,Name,Amount)
SELECT 1,
CASE
WHEN Amount IS NULL or Amount = 0 THEN TableA.CustomerName
ELSE TableB.CustomerName
END,
Amount
FROM TableA, TableB
-- need a WHERE clause here to get TableA/TableB records, and you need to make
-- sure you join them properly
Pretty close to #dcp answer, instead using a sub query in the case statement.
INSERT #CustomTable
(
id,
Name,
Amount
)
SELECT
1,
CustomerName,
CASE
WHEN ISNULL(TableB.Amount,0) > 0 THEN TableB.Amount
ELSE (SELECT TableA.Amount FROM TableA WHERE 1 = 1) --Replace logic to get value from TableA
END AS Amount
FROM TableB