If I have a query like this
SELECT * FROM table1 WHERE col1 IN ({SUBS})
Is there anything I can replace {SUBS} with that will return all rows in the table?
Further details:
I am building the SQL dynamically in my app, so I cannot (should not) edit other parts of the query except what's in braces. So,
SELECT * FROM table1
will not do.
Also,
SELECT * FROM table1 WHERE col1 IN (SELECT col1 FROM table1)
would be hackish and highly inefficient. Consider the table have more than 50k rows.
This would do it:
select col1 from table1
Edit: There seems to be a bit of confusion - the OP asked what value could be used to replace {SUBS} that would return all rows from table1. My answer above is what you could use in place of {SUBS} that would return all the rows.
This works for me in SQL Server:
SELECT * FROM INFORMATION_SCHEMA.COLUMNS
WHERE COLUMN_NAME IN (COLUMN_NAME)
Have you tried just using COL1 for {SUBS}?
e.g.
SELECT * FROM table1 WHERE col1 IN (col1)
If you replaced {SUBS} with SELECT col1 FROM table1, you would end up with
SELECT * FROM table1 WHERE col1 IN (SELECT col1 FROM table1);
which would return all rows from table1. This is, of course, simply a more roundabout way of saying:
SELECT * FROM table1;
You're right,
SELECT * FROM table1 WHERE col1 IN (SELECT col1 FROM table1)
does work, but is highly inefficient; requiring a merge join to return all rows.
Use the following which is just as efficient as regular SELECT * FROM table1
SELECT * FROM table1 WHERE col1 IN (col1)
However, that said; I suggest you have a chat to the person who is trying to impose the SELECT * FROM table1 WHERE col1 IN ({SUBS}) structure. There is no good reason to do so.
It unnecessarily complicates queries.
Creates risk of highly inefficient queries.
Potentially even limits developers to use certain techniques.
I suspect the person imposing this is trying to implement some sort of silver-bullet framework. Remember, the golden rule in software development is that there are no silver-bullets.
If you're simply trying to retrieve every row in the table, then:
select * from table1
If you're trying to prove a point or win a bet or something, then:
select * from table1 where col1 in (select col1 from table1)
If the query requires some WHERE condition, then I would try to replace it with an EXISTS statement:
select
*
from
table1 t1
where
exists ( {subs} )
Then {subs} can be replaced with any expression that does not yield NULL.
This works in Oracle:
select * from table1 where col1 in (col1)
Related
I want to know if it's possible to make a where clause compare 2 columns to the same subquery. I know I could make a temp table/ variable table or write the same subquery twice. But I want to avoid all that if possible. The Subquery is long and complex and will cause significant overhead if I have to write it twice.
Here is an example of what I am trying to do.
SELECT * FROM Table WHERE (Column1 OR Column2) IN (Select column from TABLE)
I'm looking for a simple answer and that might just be NO but if it's possible without anything too elaborate please clue me in.
I updated the select to use OR instead of AND as this clarified my question a little better.
The example you've given would probably perform best using exists, such as:
select *
from t1
where exists (
select 1 from t2
where t2.col = t1.col1 and t2.col = t1.col2
);
To prevent writing the complicated subquery twice, you can use a CTE (Common Table Expression):
;WITH MyFirstCTE (x) AS
(
SELECT [column] FROM [TABLE1]
-- add all the very complicated stuff here
)
SELECT *
FROM Table2
WHERE Column1 IN (SELECT x FROM MyFirstCTE)
AND Column2 IN (SELECT x FROM MyFirstCTE)
Or using EXISTS:
;WITH MyFirstCTE (x) AS
(
SELECT [column] FROM [TABLE1]
-- add all the very complicated stuff here
)
SELECT *
FROM Table2
WHERE EXISTS (SELECT 1 FROM MyFirstCTE WHERE x = Column1)
AND EXISTS (SELECT 1 FROM MyFirstCTE WHERE x = Column2)
I used deliberately clumsy names, best to pick better ones.
I started it with a ; because if it's not the first command in a larger script then a ; is needed to separate the CTE from the commands before it.
I am trying to use a common table expression in my INSERT.
When I do:
with A as (select col1,col2 from table1) select * from A
it works
But when I do:
with A as (select col1,col2 from table1)
insert into table2 (col1,col2) (select col1,col2 from A)
I get:
found "INSERT" (at char XXXXX) expecting `SELECT' or `'(''
Your query should work with most databases. However, Oracle and earlier versions of Postgres put the CTE next to the select. So, if you are using Oracle, earlier versions of Postgres or Postgres-derived databases:
insert into table2 (col1, col2)
with A as (select col1, col2 from table1)
select col1, col2 from A;
Also, there is no need for parentheses around the select query. It isn't a subquery.
I would like to pull all of the columns from my second select statement and put it to the right of all of my columns from my first statement.
I have tried Union and the join commands with no luck.
When I use these they just have what I wanted from my first select statement.
Here is basic code I have.
Select * from MTG_TREND where LINEID='A2' end;
Select * from MTG_TREND where LINEID='B2'
All of the other columns are the same.
Select t1.*,t2.* from MTG_TREND t1
left join (
Select * from MTG_TREND where LINEID='B2'
) as t2
on t1.primarykey=t2.primarykey
where t1.LINEID='A2'
NOTE:
- Make sure you are matching the same number of columns in both SELECT Statement.
- Another thing to remember is you have to have the same matched column (datatype).
- If there are some columns that are not present is the table then just defined the column with null so that you can get it in output from another select statement.
Select col1, col2, col3,...... from MTG_TREND where LINEID='A2'
UNION ALL
Select col1, col2, col3,...... from MTG_TREND where LINEID='B2'
So for each distinct value in a column of one table I want to insert that unique value into a row of another table.
list = select distinct(id) from table0
for distinct_id in list
insert into table1 (id) values (distinct_id)
end
Any ideas as to how to go about this?
Whenever you think about doing something in a loop, step back, and think again. SQL is optimized to work with sets. You can do this using a set-based query without the need to loop:
INSERT dbo.table1(id) SELECT DISTINCT id FROM dbo.table0;
There are some edge cases where looping can make more sense, but as SQL Server matures and more functionality is added, those edge cases get narrower and narrower...
insert into table1 (id)
select distinct id from table0
The following statement works with me.
insert into table1(col1, col2) select distinct on (col1) col1 col2 from table0
The below query will also check the existing data in the Table2.
INSERT INTO Table2(Id) SELECT DISTINCT Id FROM Table1 WHERE Id NOT IN(SELECT Id FROM Table2);
Other Simple way to copy distinct data with multiple columns from one table to other
Insert into TBL2
Select * from (Select COL1, ROW_NUMBER() over(PARTITION BY COL1 Order By COL1) AS COL2 From TBL1)T
where T.COL2 = 1
I have two tables with the same columns, and I need to copy one table's rows to the other table's rows to create one big table with all the values from both tables. Right now I am doing this query to return the same thing:
SELECT col1, col2, col3 from Table1
union
SELECT col1, col2, col3 from Table2
However, it seems horribly inefficient, and on my system is very slow (returns 1210189 records).
May it work to just do:
SELECT col1, col2, col3
INTO Table1
FROM Table2
Start with union all:
select col1, col2, col3 from Table1
union all
select col1, col2, col3 from Table2
Your query is trying to deduplicate things, which would slow it down considerably.
I think the best option is to create a view in sql server, this will optimize the performance of the query:
SELECT col1, col2, col3 from Table1
union all
SELECT col1, col2, col3 from Table2
(As other users said: "union" is used to select distinct values from two tables
where as "union all" is used to select all values including
duplicates from the tables.)
At the same time I would restrict the number of rows I get from the database if i am writing them for a web and if this is giving me problems, with the new functions of Sql Server 2005 row_number(), with this I would page results.
You could use this to fill the second table:
Insert into table2 select * from table1;
Or if you want to be more specific:
Insert into table2(col1, col2, col3) select col1, col2, col3 from table1;
(Note: some DBMSs might require putting parenthesis around the SELECT clause.)
select * into new table(your new table name)
from table1.col1,table1.col2,table2.col1;
here columns can be your required columns .
select * into newtable from table1
union all
select * from table2
Worked well. Guidelines, both tables have exact same column names :)