(SELECT CONCAT('ABCDE',SUM((SELECT MAX(id) FROM optigo_data.admin_userdetails LIMIT 1)+1)))
Above is working in Mysql but its not working in Impala/Hive, please help me out.
Error: sub query is not supported.
Reason for this error is that Impala only supports subqueries in the FROM and WHERE clause.
I think this would be the impala equivalent:
SELECT
CONCAT('ABCDE',cast(SUM(t.value+1) as string))
from
(SELECT MAX(cast(id as int)) as value
FROM optigo_data.admin_userdetails LIMIT 1) as t
But looking at the query assuming your goal is to produce a string containing the highest ID + 1, a simpler solution would be:
SELECT
CONCAT('ABCDE',cast(MAX(cast(id as int)+1) as string))
FROM optigo_data.admin_userdetails
Please correct me if my assumption is incorrect. You can drop the cast as int if id is already in numeric format.
Related
Edit: Answer is to use MIN. it works on both strings & numbers. Credit to #cadet down below.
Original question:
I've been reading through similar questions around this for the last half an hour and cannot understand the responses so let me try to get a simple easy to follow answer.
What is the PostgresSQL equivalent to this code which I would write if I were using SQL Server, to bring back the first value in field2 when aggregating:
Select field1, first(field2) from table group by field1?
I have read that DISTINCT ON is the right thing to use? In that case would it be:
Select field1, DISTINCT ON(field2) from table group by field1? because that gives me a syntax error
Edit:
Here is the error stating that the FIRST function does not exist in PostGresSQL:
ERROR: function first(asset32type) does not exist
LINE 1: Select policy, first (name) from multi_asset group by policy...
^
HINT: No function matches the given name and argument types. You might need to add explicit type casts.
SQL state: 42883
Character: 16
And in case it isn't already clear when I say that in SQL Server the first() function brings back the first value in field2 when aggregating, I mean if you had data like this:
field1
field2
Tom
32
Tom
53
Then select field1, first(field2) group by field1 would give you back:
Tom, 32 - i.e. it picks the first value from field2
Maybe this one, using DISTINCT ON():
SELECT DISTINCT ON (field1)
field1
, field2
FROM table
ORDER BY
field1
, field2;
But without any data or any example, it's just a wild guess.
If first is related with specific order
select distinct field1,
first_value(field2)
over (partition by field1 order by field2) from
(
values (1,10),(1,11),(1,12),(2,23),(2,24)
) as a(field1,field2)
If first is just minimum or maximum
select field1,
min(field2)
from
(
values (1,10),(1,11),(1,12),(2,23),(2,24)
) as a(field1,field2)
group by field1
Relatively new SQL user question....
If my postgresql query looks like this:
select
to_timestamp((unnest(enrolled_ranges) ->> 'start_time')::float) as start_time
, to_timestamp((unnest(enrolled_ranges) ->> 'end_time')::float) as end_time
from student_inclusions
where student_id = '123456'
And the initial enrolled_ranges json data is this:
{"{\"start_time\":1536652800.00007,\"end_time\":1563981839.966626}","{\"start_time\":1563982078.624668,\"end_time\":1563989693.830777}"}
Why does sql do this
instead of this
The first answer is what I want, I just don't understand how sql knows from the query to associate the matching start and end times. Do you have any insight?
The documentation on set-returning functions describes the behavior you observed:
For each row from the underlying query, there is an output row using the first result from each set-returning function, then an output row using the second result, and so on.
See also What is the expected behaviour for multiple set-returning functions in SELECT clause?
Is there a way to use the results of a function call in the order by clause?
My current attempt (I've also tried some slight variations).
SELECT it.item_type_id, it.asset_tag, split_part(it.asset_tag, 'ASSET', 2)::INT as tag_num
FROM serials.item_types it
WHERE it.asset_tag LIKE 'ASSET%'
ORDER BY split_part(it.asset_tag, 'ASSET', 2)::INT;
While my general assumption is that this can't be done, I wanted to know if there was a way to accomplish this that I wasn't thinking of.
EDIT: The query above gives the following error [22P02] ERROR: invalid input syntax for integer: "******"
Your query is generally OK, the problem is that for some row the result of split_part(it.asset_tag, 'ASSET', 2) is the string ******. And that string cannot be cast to an integer.
You may want to remove the order by and the cast in the select list and add a where split_part(it.asset_tag, 'ASSET', 2) = '******', for instance, to narrow down that data issue.
Once that is resolved, having such a function in the order by list is perfectly fine. The quoted section of the documentation in the comments on the question is referring to applying an order by clause to the results of UNION, INTERSECTION, etc. queries. In other words, the order by found in this query:
(select column1 as result_column1 from table1
union
select column2 from table 2)
order by result_column1
can only refer to the accumulated result columns, not to expressions on individual rows.
I'm sorry for my title, but it's totally right. I don't know PostgreSQL well, but I have to take over other person's application. I know SQL, so it's usually no problem to take over any application based on MSSQL, Oracle, MySQL, PostgreSQL, ... but here is some kind of PostgreSQL facet. Could anyone, please, explain this query to me?
select company_generate_course_template_fc
((select company_id from company order by 1 desc limit 1)::int)
The query calls the function company_generate_course_template_fc() passing the result of the query: select company_id from company order by 1 desc limit 1 as an argument. The result is cast to an integer using ::int (see the manual for details)
Apart from the ::int part (and the different ways of limiting the result to a single row), this wouldn't be much different in other databases
The ANSI SQL equivalent of ::int would be cast(... as integer)
If you are talking about ::int it's type casting from string (company_id) to integer value
I thought I understood how I can do a SELECT from the results of another SELECT statement, but there seems to be some sort of blurring of scope that I don't understand. I am using SQL Server 2008R2.
It is easiest to explain with an example.
Create a table with a single nvarchar column - load the table with a single text value and a couple of numbers:
CREATE TABLE #temptable( a nvarchar(30) );
INSERT INTO #temptable( a )
VALUES('apple');
INSERT INTO #temptable( a )
VALUES(1);
INSERT INTO #temptable( a )
VALUES(2);
select * from #temptable;
This will return: apple, 1, 2
Use IsNumeric to get only the rows of the table that can be cast to numeric - this will leave the text value apple behind. This works fine.
select cast(a as int) as NumA
from #temptable
where IsNumeric(a) = 1 ;
This returns: 1, 2
However, if I use that exact same query as an inner select, and try to do a numeric WHERE clause, it fails saying cannot convert nvarchar value 'apple' to data type int. How has it got the value 'apple' back??
select
x.NumA
from
(
select cast(a as int) as NumA
from #temptable
where IsNumeric(a) = 1
) x
where x.NumA > 1
;
Note that the failing query works just fine without the WHERE clause:
select
x.NumA
from
(
select cast(a as int) as NumA
from #temptable
where IsNumeric(a) = 1
) x
;
I find this very surprising. What am I not getting? TIA
If you take a look at the estimated execution plan you'll find that it has optimized the inner query into the outer and combined the WHERE clauses.
Using a CTE to isolate the operations works (in SQL Server 2008 R2):
declare #temptable as table ( a nvarchar(30) );
INSERT INTO #temptable( a )
VALUES ('apple'), ('1'), ('2');
with Numbers as (
select cast(a as int) as NumA
from #temptable
where IsNumeric(a) = 1
)
select * from Numbers
The reason you are getting this is fair and simple. When a query is executed there are some steps that are being followed. This is a parse, algebrize, optimize and compile.
The algebrize part in this case will get all the objects you need for this query. The optimize will use these objects to create a best query plan which will be compiled and executed...
So, when you look into that part you will see it will do a table scan on #temptable. And #temptable is defined as the way you created your table. That you will do some compute on it is a different thing..... The column still has the nvarchar datatype..
To know how this works you have to know how to read a query. First all the objects are retrieved (from table, inner join table), then the predicates (where, on), then the grouping and such, then the select of the columns (with the cast) and then the orderby.
So with that in mind, when you have a combination of selects, the optimizer will still process it that way.. since your select is subordinate to the from and join parts of your query, it will be a reason for getting this error.
I hope i made it a little clear?
The optimizer is free to move expressions in the query plan in order to produce the most cost efficient plan for retrieving the data (the evaluation order of the predicates is not guaranteed). I think using the case expression like bellow produces a NULL in absence of the ELSE clause and thus takes the APPLE out
select a from #temptable where case when isnumeric(a) = 1 then a end > 1