I'm thinking about a SQL query that returns me all entries from a column whose first 5 characters match. Any ideas?
I'm thinking about entries where ANY first 5 characters match, not specific ones. E.g.
HelloA
HelloB
ThereC
ThereD
Something
would return the first four entries:
HelloA
HelloB
ThereC
ThereD
EDIT: I am using SQL92 so cannot use the left command!
Try this :
SELECT *
FROM YourTable
WHERE LEFT(stringColumn, 5) IN (
SELECT LEFT(stringColumn, 5)
FROM YOURTABLE
GROUP BY LEFT(stringColumn, 5)
HAVING COUNT(*) > 1
)
SQLFIDDLE DEMO
This selects the first 5 characters, groups by them and returns only the ones that happen more than once.
Or with Substring:
SELECT * FROM YourTable
WHERE substring(stringColumn,1,5) IN (
SELECT substring(stringColumn,1,5)
FROM YOURTABLE
GROUP BY substring(stringColumn,1,5)
HAVING COUNT(*) > 1)
;
SQLFIDDLE DEMO
Sounds easy enough...
In SQL Server this would be something along the lines of
where Left(ColumnName,5) = '12345'
Try
Select *
From tbl t1
Where exists (
Select 1
From tbl t2
Where left(t1.str, 5) = left(t2.str)
Group by left(t2.str, 5)
Having count(1) > 1
)
You didn't specify your DBMS. If it supports Windowed Aggregate functions it's:
select *
from
(
select
tab.*,
count(*) over (partition by substring(col from 1 for 5) as cnt
from tab
) as dt
where cnt > 1
You want to work with a CTE approach.
Something like this:
with CountriesCTE(Id, Name)
as (
select Id, Name from Countries
)
select distinct Countries.Name
from CountriesCTE, Countries
where left(CountriesCTE.Name,5) = left(Countries.Name,5) and CountriesCTE.Id <> Countries.Id
Related
I have a database of more than 10,000 rows. eg:
id text
1 abc
2 ghj
3 cde
4 hif
5 klm
6 bbc
7 jkl
8 mno
9 dbo
10 ijk
I need to fetch the next three rows where the text matches a condition.
For eg: if I am doing a text like '%bc% query it should return me rows with ids 1,2,3,4,6,7,8,9 as row #1 and #6 is a match
Use below query to get the desired result. I am assuming you want to calculate next based on ID only and ID is always increment by 1, as you have mentioned in question.
If ID doesn't always increment by 1 , then first add a ROW Number and then replace id in t2 subquery and join condition with row number.
select t1.id, t1.id_text
from test t1
join
(
select id from test where id_text like '%bc%'
UNION
select id+1 from test where id_text like '%bc%'
UNION
select id+2 from test where id_text like '%bc%'
UNION
select id+3 from test where id_text like '%bc%'
) t2
on t1.id = t2.id;
SQL Fiddle Link
with -- Test data
t(i, x) as (values
(1,'abc'),(2,'ghj'),(3,'cde'),(4,'hif'),(5,'klm'),(6,'bbc'),(7,'jkl'),(8,'mno'),(9,'dbo'),(10,'ijk'))
select r.*
from
t as t0 cross join lateral (
select *
from t
where t.i >= t0.i
order by t.i
limit 4) as r
where t0.x like '%bc%'
order by r.i;
Lateral joins allows to use previous table in the next subquery.
You could use something like this:
SELECT next.*
FROM test, test next
WHERE test.text LIKE '%bc%'
AND (test.id + 1 = next.id OR test.id + 2 = next.id OR test.id + 3 = next.id)
I am not going to assume that the ids have no gaps. One method uses lag():
select t.*
from (select t.*,
lag(text) over (order by id) as prev_text,
lag(text, 2) over (order by id) as prev_text2,
lag(text, 3) over (order by id) as prev_text3
from t
) t
where text like '%bc%' or
prev_text like '%bc%' or
prev_text2 like '%bc%' or
prev_text3 like '%bc%';
You can also do this with one comparison, using other window functions:
select id, text
from (select t.*,
sum( (text like '%bc%')::int ) over (order by id rows between 3 preceding and current row) as cnt
from t
) t
where cnt > 0;
With an index on id, this might be the fastest approach to solving the problem.
SELECT AS, COUNT(*)
FROM Table1
HAVING COUNT(AS)>1
group BY AS;
This produces the result
AS COUNT
5 2
I then want to use the AS value in another query and only output the end result. Is this possible.i was thinking something like.
SELECT *
FROM
TABLE 2
Where AS =(
SELECT AS, COUNT(*)
FROM Table1
HAVING COUNT(AS)>1
group BY AS;
);
This is called a subquery. To be safe, you would use in instead of = (and as is a bad name for a column, because it is a SQL key word):
SELECT *
FROM TABLE2
WHERE col IN (SELECT col
FROM Table1
GROUP BY col
HAVING COUNT(col) > 1
);
Your first query is also incorrect, because the having clause goes after the group by.
You could use a subquery with the in operator:
SELECT *
FROM table2
WHERE AS IN (SELECT AS
FROM table1
GROUP BY AS
HAVING COUNT(*) > 1)
I want to do the following query, how can I implement it?
SELECT * FROM table WHERE routeNum LIKE 'N10%'
-->if no rows return, WHERE clause change to routeName LIKE '&something%'
I think this will work for you:
WITH CTE AS (
SELECT 2 AS 'INDEX', * FROM table WHERE routeNum LIKE 'N10%'
UNION ALL
SELECT 1 AS 'INDEX', * FROM table WHERE routeNum LIKE '&something%'
)
SELECT *
FROM CTE
WHERE CTE.INDEX = (SELECT MAX(INDEX) FROM CTE)
As you have to choose between two result sets, you will need two queries, which will return two different sets and then, based on the 'index' which corresponds to the query that has run, you choose how to display your results.
Here is a SQLFiddle demo.
A possible solution
WITH cte AS
(
SELECT *
FROM routes
WHERE routeNum LIKE 'N10%'
)
SELECT * FROM cte
UNION ALL
SELECT * FROM routes
WHERE routeNum LIKE 'something else%'
AND NOT EXISTS
(
SELECT *
FROM cte
)
Here is SQLFiddle demo
WITH tmp AS
(
SELECT t.*,
CASE
WHEN routeNum LIKE 'N10%' THEN 1
WHEN routeNum LIKE '&something%' THEN 2
ELSE 3 END AS q
FROM table t
)
SELECT * FROM tmp t
WHERE q = CASE WHEN (SELECT COUNT(*) FROM tmp WHERE q = 1 ) > 0 THEN 1 ELSE 2 END
What is the method in T-SQL to select the orginal values limited by a HAVING attribute. For example, if I have
A|B
10|1
11|2
10|3
How would I get all the values of B (Not An Average or some other summary stat), Grouped by A, having a Count (Occurrences of A) greater than or equal two 2?
Actually, you have several options to choose from
1. You could make a subquery out of your original having statement and join it back to your table
SELECT *
FROM YourTable yt
INNER JOIN (
SELECT A
FROM YourTable
GROUP BY
A
HAVING COUNT(*) >= 2
) cnt ON cnt.A = yt.A
2. another equivalent solution would be to use a WITH clause
;WITH cnt AS (
SELECT A
FROM YourTable
GROUP BY
A
HAVING COUNT(*) >= 2
)
SELECT *
FROM YourTable yt
INNER JOIN cnt ON cnt.A = yt.A
3. or you could use an IN statement
SELECT *
FROM YourTable yt
WHERE A IN (SELECT A FROM YourTable GROUP BY A HAVING COUNT(*) >= 2)
A self join will work:
select B
from table
join(
select A
from table
group by 1
having count(1)>1
)s
using(A);
You can use window function (no joins, only one table scan):
select * from (
select *, cnt=count(*) over(partiton by A) from table
) as a
where cnt >= 2
In Microsoft SQL Server 2005 or above, I would like to get the first row, and if there is no matching row, then return a row with default values.
SELECT TOP 1 ID,Name
FROM TableName
UNION ALL
SELECT 0,''
ORDER BY ID DESC
This works, except that it returns two rows if there is data in the table, and 1 row if not.
I'd like it to always return 1 row.
I think it has something to do with EXISTS, but I'm not sure.
It would be something like:
SELECT TOP 1 * FROM Contact
WHERE EXISTS(select * from contact)
But if not EXISTS, then SELECT 0,''
What happens when the table is very full and you might want to specify which row of your top 1 to get, such as the first name? OMG Ponies' query will return the wrong answer in that case if you just change the ORDER BY clause. His query also costs about 8% more CPU than this modification (though it has equal reads)
SELECT TOP 1 *
FROM (
SELECT TOP 1 ID,Name
FROM TableName
ORDER BY Name
UNION ALL
SELECT 0,''
) X
ORDER BY ID DESC
The difference is that the inner query has a TOP 1 also, and which TOP 1 can be specified there (as shown).
Just for fun, this is another way to do it which performs very closely to the above query (-15ms to +30ms). While it's more complicated than necessary for such a simple query, it demonstrates a technique that I don't see other SQL folks using very often.
SELECT
ID = Coalesce(T.ID, 0),
Name = Coalesce(T.Name, '')
FROM
(SELECT 1) X (Num)
LEFT JOIN (
SELECT TOP 1 ID, Name
FROM TableName
ORDER BY ID DESC
) T ON 1 = 1 -- effective cross join but does not limit rows in the first table
Use:
SELECT TOP 1
x.id,
x.name
FROM (SELECT t.id,
t.name
FROM TABLENAME t
UNION ALL
SELECT 0,
'') x
ORDER BY id DESC
Using a CTE equivalent:
WITH query AS (
SELECT t.id,
t.name
FROM TABLENAME t
UNION ALL
SELECT 0,
'')
SELECT TOP 1
x.id,
x.name
FROM query x
ORDER BY x.id DESC
CREATE TABLE #sample(id INT, data VARCHAR(10))
SELECT TOP 1 id, data INTO #temp FROM #sample
IF ##ROWCOUNT = 0 INSERT INTO #temp VALUES (null, null)
SELECT * FROM #temp
put the top oustide of the UNION query
SELECT TOP 1 * FROM(
SELECT ID,Name
FROM TableName
UNION ALL
SELECT 0,''
) z
ORDER BY ID DESC
IF EXISTS ( SELECT TOP 1 ID, Name FROM TableName )
BEGIN
SELECT TOP 1 ID, Name FROM TableName
END
ELSE
BEGIN
--exists returned no rows
--send a default row
SELECT 0, ''
END