I have two lists of values of variable but equal lengths.
Example:
vals1: a, b, c
vals2: 1, 2, 3
What is the best way to do something equivalent to:
select * from table where (col1=vals1[0] and col2=vals2[0]) or (col1=vals1[1] and col2=vals2[1]) or (col1=vals1[2] and col2=vals2[2])
Keeping in mind that the length of the lists can be 1 or more and always the same length. I'd love to not loop and build the string if another option exists (preferably in the form of a SQL query). Any help would be appreciated, thanks.
unnest the arrays in parallel
select *
from t
where (col1, col2) in (
select (a,b)
from (
select unnest(array['a','b','c']), unnest(array[1,2,3])
) s (a,b)
)
Related
I have a Redshift table with the following column
How can I extract the value starting by cat_ from this column please (there is only one for each row and at different position in the array)?
I want to get those results:
cat_incident
cat_feature_missing
cat_duplicated_request
Thanks!
There is no easy way to extract multiple values from within one column in SQL (or at least not in the SQL used by Redshift).
You could write a User-Defined Function (UDF) that returns a string containing those values, separated by newlines. Whether this is acceptable depends on what you wish to do with the output (eg JOIN against it).
Another option is to pre-process the data before it is loaded into Redshift, to put this information in a separate one-to-many table, with each value in its own row. It would then be trivial to return this information.
You can do this using tally table (table with numbers). Check this link on information how to create this table: http://www.sqlservercentral.com/articles/T-SQL/62867/
Here is example how you would use it. In real life you should replace temporary #tally table with a permanent one.
--create sample table with data
create table #a (tags varchar(500));
insert into #a
select 'blah,cat_incident,mcr_close_ticket'
union
select 'blah-blah,cat_feature_missing,cat_duplicated_request';
--create tally table
create table #tally(n int);
insert into #tally
select 1
union select 2
union select 3
union select 4
union select 5
;
--get tags
select * from
(
select TRIM(SPLIT_PART(a.tags, ',', t.n)) AS single_tag
from #tally t
inner join #a a ON t.n <= REGEXP_COUNT(a.tags, ',') + 1 and n<1000
)
where single_tag like 'cat%'
;
Thanks!
In the end I managed to do it with the following query:
SELECT SUBSTRING(SUBSTRING(tags, charindex('cat_', tags), len(tags)), 0, charindex(',', SUBSTRING(tags, charindex('cat_', tags), len(tags)))) tags
FROM table
I have an SQLite query where I need the ability to get rows where a certain column (A, below) can either be anything (aka wildcard) or 1 of several options.
This works for wildcard or single values, but not multiple:
SELECT * FROM table WHERE A LIKE "%"
SELECT * FROM table WHERE A LIKE "1"
This works for single or multiple values, but not wildcard:
SELECT * FROM table WHERE A IN (1)
SELECT * FROM table WHERE A IN (1, 2, 3)
What I would want to be able to do is something like this:
SELECT * FROM table WHERE A IN (%)
I could use an if statement to choose between the first two options, except I actually have a lot of columns where I need to do this, more like:
SELECT * FROM table WHERE A IN (1, 2, 3) AND B IN (4, 5, 6) AND C IN (%) AND D IN (7, 8)
So nested "if" loops get pretty unwieldy.
So, is there a way to use a wildcard with WHERE IN or a way to have multiple possibilities in WHERE LIKE?
If column is defined as NOT NULL you could use:
SELECT * FROM table WHERE A IN (A);
--for not nullable column it's equivalent of 1=1
DBFiddle Demo
I have a SQL table as shown below. I want to generate strings using the 2 fields in my table.
A B
M1 tiger
M1 cat
M1 dog
M3 lion
I want to read in this table, count the number of rows, and store it in string variables like String1 = M1_tiger, String2 = M1_cat, etc. What's the best way to do this?
You could do a concat type query.
SELECT (Table.A + '_' + Table.B) AS A_B, COUNT(*) AS RowsCount FROM Table
I'm asuming the your table name is "Table", the result where you will find the strings you want would be the column named A_B, each record will have two things in each record, one would be the string you asked for, the other column would always be the same thing, the total number of records on you table.
The count part is kinda easy but check this link so you can use the specific count you need: http://www.w3schools.com/sql/sql_func_count.asp
You can try this:
SELECT CONCAT(A, '_', B) FROM yourtable
When you say "read in this table", do you mean read it into a programming language like C#? Or do you want to dynamically create sql variables?
You may want to use a table variable to store your strings rather than individual variables. Regarding getting the row number, you could use something like:
WITH CTE AS
(
SELECT A, B,
ROW_NUMBER() OVER (order by OrderDate) AS 'RowNumber'
FROM MyTable
)
SELECT A,B,RowNumber FROM CTE
See this answer for more on how you may choose to use the table variable.
SQL: Dynamic Variable Names
If your are using Oracle, you can also do it like:
select A ||'_'||B
from yourTable
Solution for PostgreSQL
CREATE SEQUENCE one;
SELECT array_to_string(array_agg(concat('String',nextval('one'),' = ',A,'_',B)), ', ')
AS result
FROM test_table;
DROP SEQUENCE one;
Explanation:
Create a temporary sequence 'one' in order to use nextval function.
nextval('sequence') - advance sequence and return new value.
concat('input1', ...) - concatenate all arguments.
array_agg('input1', ...); - input values, including nulls,
concatenated into an array.
array_to_string('array', 'delimiter') - concatenates array elements
using supplied delimiter and optional null string.
Drop the sequence 'one'.
The output of the query (for two test rows in test_table):
result
-------------------------------------------
String1 = M1_tiger, String2 = M1_cat
(1 row)
Is it possible in oracle sql to return a default row if no rows found.
I have a process where in rows fetched will be put in a flat ascii file.
now i have a requirement that if there are no rows fetched by the sql query then there should be a default row in the ascii file.
is it possible in sql to output a default row if no rows fetched by the query
note: i dont want to use pl/sql.
For complex queries where the overhead on finding out if there is a row in the result set is onerous or the query is just very large and unwieldy, then a subquery factoring clause might be beneficial:
With my_query as
(
select a, b, c from foobar where foo='FOO'
)
Select a,b,c
From my_query
Union All
Select ...
From dual
Where Not Exists
(Select 1 from my_query)
/
You could use UNION ALL for this:
select a, b, c from foobar
where foo='FOO'
union all
select 'def', 'ault', 'value' from dual
where not exists ( select 'x' from foobar where foo='FOO' )
I suspect that it would be cleaner to have the process that the writes the ASCII file write the default data if no rows are returned rather than getting Oracle to do it. If the query that you're using is expensive, you'd significantly increase that cost if you fudge it to return a default row as ammoQ and David Oniell have done.
There is another (sad, twisted) option. No CTEs or subquery repetition needed.
select
coalesce(a, 'def'),
coalesce(b, 'ault'),
coalesce(c, 'value')
from foobar
right join (select 1 from dual) on 1=1
where foobar.some_condition;
I'm looking for the best way to select numbers directly from an in clause.
Basically like:
SELECT * FROM (2,6,1,8);
That doesn't work. I can do it this way:
SELECT Lv FROM ( SELECT Level LV
FROM DUAL
CONNECT BY Level < 20)
WHERE Lv IN (2,6,1,8);
But that seems to be a bit clunky. Is there a more elegant way?
You can do
select column_value from table(sys.dbms_debug_vc2coll(1,2,3,4,5));
but that actually returns a varchar2. You can create your own TYPE and use that
create type tab_num is table of number;
/
select column_value from table(tab_num(1,2,3,4,5));
It's also worth looking at the MODEL clause. It looks complicated, but it is very good at generating data
SELECT x from dual
MODEL DIMENSION BY (1 AS z) MEASURES (1 x)
RULES ITERATE (7) (x[ITERATION_NUMBER]=ITERATION_NUMBER+1)
It's more elegant if you materialize an auxiliary numbers table:
SELECT num FROM numbers WHERE num IN (2,6,1,8);
And this is also useful when combined with another table.
For instance, I've had a case where I needed to populate large configuration tables with changes from piecewise results:
Big SP or Excel sheet or report identifies missing cost centers in config gives a large set of results which need to be inserted with varying data in some groups.
Paste partial results into a individual comma separated lists:
INSERT INTO {stuff}
SELECT {stuff}, 130 as line_item
FROM numbers
WHERE numbers.num IN ({pasted a section of results})
INSERT INTO {stuff}
SELECT {stuff}, 135 as line_item
FROM numbers
WHERE numbers.num IN ({pasted another section of results})
If you don't explicitly need the IN clause, you could use UNION:
select 2 from dual
union
select 6 from dual
union
select 1 from dual
union
select 8 from dual
There is a more elegant variant to INSERT multiple rows into a table:
INSERT ALL
INTO table (col) VALUES ('a')
INTO table (col) VALUES ('b')
INTO table (col) VALUES ('c')
SELECT * FROM dual;
But I don't know a way to do that for a SELECT.