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Select statement in SQLite recognizing row number
For example, SELECT * FROM table WHERE [row] BETWEEN x AND y
How can this be done? I've done some reading but haven't found anything specifically correct.
Imagine a list where you want results paged by an X amount of results, so for page 10 you would need results from rows 10 * X to 10 * X + X. Rather than display ALL results in one go
For mysql you have limit, you can fire query as :
SELECT * FROM table limit 100` -- get 1st 100 records
SELECT * FROM table limit 100, 200` -- get 200 records beginning with row 101
For Oracle you can use rownum
See mysql select syntax and usage for limit here.
For SQLite, you have limit, offset. I haven't used SQLite but I checked it on SQLite Documentation. Check example for SQLite here.
Following your clarification you're looking for limit:
SELECT * FROM `table` LIMIT 0, 10
This will display the first 10 results from the database.
SELECT * FROM `table` LIMIT 5, 5 .
Will display 5-9 (5,6,7,8,9)
The syntax follows the pattern:
SELECT * FROM `table` LIMIT [row to start at], [how many to include] .
The SQL for selecting rows where a column is between two values is:
SELECT column_name(s)
FROM table_name
WHERE column_name
BETWEEN value1 AND value2
See: http://www.w3schools.com/sql/sql_between.asp
If you want to go on the row number you can use rownum:
SELECT column_name(s)
FROM table_name
WHERE rownum
BETWEEN x AND y
However we need to know which database engine you are using as rownum is different for most.
You can use rownum :
SELECT * FROM table WHERE rownum > 10 and rownum <= 20
Using Between condition
SELECT *
FROM TEST
WHERE COLUMN_NAME BETWEEN x AND y ;
Or using Just operators,
SELECT *
FROM TEST
WHERE COLUMN_NAME >= x AND COLUMN_NAME <= y;
Assuming id is the primary key of table :
SELECT * FROM table WHERE id BETWEEN 10 AND 50
For first 20 results
SELECT * FROM table order by id limit 20;
Have you tried your own code?
This should work:
SELECT * FROM people WHERE age BETWEEN x AND y
Use the LIMIT clause:
/* rows x- y numbers */
SELECT * FROM tbl LIMIT x,y;
refer : http://dev.mysql.com/doc/refman/5.0/en/select.html
Related
We would expect that this Google BigQuery query would remove at most 10 rows of results - but this query gives us zero results - despite that table A has thousands of rows all with unique ENCNTR_IDs.
SELECT ENCNTR_ID
FROM `project.dataset.table_A`
WHERE ENCNTR_ID NOT IN
(
SELECT ENCNTR_ID
FROM `project.dataset.table_B`
LIMIT 10
)
If we make the query self-referential, it behaves as expected: we get thousands of results with just 10 rows removed.
SELECT ENCNTR_ID
FROM `project.dataset.table_A`
WHERE ENCNTR_ID NOT IN
(
SELECT ENCNTR_ID
FROM `project.dataset.table_A` # <--- same table name
LIMIT 10
)
What are we doing wrong? Why does the first query give us zero results rather than just remove 10 rows of results?
Solution: Use NOT EXISTS instead of NOT IN when dealing with possible nulls:
SELECT *
FROM UNNEST([1,2,3]) i
WHERE NOT EXISTS (SELECT * FROM UNNEST([2,3,null]) i2 WHERE i=i2)
# 1
Previous guess - which turned out to be the cause:
SELECT *
FROM UNNEST([1,2,3]) i
WHERE i NOT IN UNNEST([2,3])
# 1
vs
SELECT *
FROM UNNEST([1,2,3]) i
WHERE i NOT IN UNNEST([2,3,null])
# This query returned no results.
Are there any nulls in that project.dataset.table_B?
order by has only one reducer, so slow.I'm trying to find a fast way.sort by sorts in each reducer,then how can we get global ordering?
I got this by search engine:
select * from
(select title,cast(price as FLOAT) p from tablename
distribute by time
sort by p desc
limit 10 ) t
order by t.p desc
limit 10;
Then try to validate it.
1.Get right answer in my hive table.There are 215666 records in the table named tablename.
SELECT title,cast(price as FLOAT) p
from tablename
WHERE dt='2020-03-08'
and price IS NOT NULL
ORDER BY p DESC
LIMIT 10
;
2.Use the searched clause.
set hive.execution.engine=mr;
set mapred.reduce.tasks=5;
SELECT title,cast(price as FLOAT) p
from tablename
WHERE dt='2020-03-08'
and price IS NOT NULL
DISTRIBUTE BY title
SORT BY p desc
LIMIT 10
;
The result is the same as the right answer!
Here are my questions:
1.Why only return 10 lines? There are 5 reducer, each reducer returns 10, should be 5*10=50?
2.If should return 10 lines, why the result is global ordering? This 10 line is not from the same reducer ? The limit is random, it cannot get global order in 5 reducer.
3.If should return 10 lines, the outer part in the searched clause is redundant?
select * from
(
) t
order by t.p desc
limit 10;
Consider using total order partitioner, see https://cwiki.apache.org/confluence/display/Hive/HBaseBulkLoad#HBaseBulkLoad-PrepareRangePartitioning for details (just ignore part with HBase)
I'm trying to get a few columns using a function F(a,b,x) from SQL Server for say 20 values. Basically it's like
SELECT
col1, col2, F(a,b,1), F(a,b,2), ... F(a,b,20)
FROM
table
Is that possible to use a loop to SELECT F(a,b,#i) where 0 < #i < 21?
Thanks!
There is no "looping" in a SQL statement. But, you can come close by doing:
select col1, col2, n.n, f(a, b, n.n)
from table t cross join
(select 1 as n union all select 2 union all select 3 . . .
select 20
) n;
The exact syntax depends on the database you are using. There are also ways to generate numbers, once again, depending on the database.
This generates 20 rows for each row in the table, rather than 20 columns. The results can be pivoted if you really need them in columns.
Supposed you have a table T(A) with only positive integers allowed, like:
1,1,2,3,4,5,6,7,8,9,11,12,13,14,15,16,17,18
In the above example, the result is 10. We always can use ORDER BY and DISTINCT to sort and remove duplicates. However, to find the lowest integer not in the list, I came up with the following SQL query:
select list.x + 1
from (select x from (select distinct a as x from T order by a)) as list, T
where list.x + 1 not in T limit 1;
My idea is start a counter and 1, check if that counter is in list: if it is, return it, otherwise increment and look again. However, I have to start that counter as 1, and then increment. That query works most of the cases, by there are some corner cases like in 1. How can I accomplish that in SQL or should I go about a completely different direction to solve this problem?
Because SQL works on sets, the intermediate SELECT DISTINCT a AS x FROM t ORDER BY a is redundant.
The basic technique of looking for a gap in a column of integers is to find where the current entry plus 1 does not exist. This requires a self-join of some sort.
Your query is not far off, but I think it can be simplified to:
SELECT MIN(a) + 1
FROM t
WHERE a + 1 NOT IN (SELECT a FROM t)
The NOT IN acts as a sort of self-join. This won't produce anything from an empty table, but should be OK otherwise.
SQL Fiddle
select min(y.a) as a
from
t x
right join
(
select a + 1 as a from t
union
select 1
) y on y.a = x.a
where x.a is null
It will work even in an empty table
SELECT min(t.a) - 1
FROM t
LEFT JOIN t t1 ON t1.a = t.a - 1
WHERE t1.a IS NULL
AND t.a > 1; -- exclude 0
This finds the smallest number greater than 1, where the next-smaller number is not in the same table. That missing number is returned.
This works even for a missing 1. There are multiple answers checking in the opposite direction. All of them would fail with a missing 1.
SQL Fiddle.
You can do the following, although you may also want to define a range - in which case you might need a couple of UNIONs
SELECT x.id+1
FROM my_table x
LEFT
JOIN my_table y
ON x.id+1 = y.id
WHERE y.id IS NULL
ORDER
BY x.id LIMIT 1;
You can always create a table with all of the numbers from 1 to X and then join that table with the table you are comparing. Then just find the TOP value in your SELECT statement that isn't present in the table you are comparing
SELECT TOP 1 table_with_all_numbers.number, table_with_missing_numbers.number
FROM table_with_all_numbers
LEFT JOIN table_with_missing_numbers
ON table_with_missing_numbers.number = table_with_all_numbers.number
WHERE table_with_missing_numbers.number IS NULL
ORDER BY table_with_all_numbers.number ASC;
In SQLite 3.8.3 or later, you can use a recursive common table expression to create a counter.
Here, we stop counting when we find a value not in the table:
WITH RECURSIVE counter(c) AS (
SELECT 1
UNION ALL
SELECT c + 1 FROM counter WHERE c IN t)
SELECT max(c) FROM counter;
(This works for an empty table or a missing 1.)
This query ranks (starting from rank 1) each distinct number in ascending order and selects the lowest rank that's less than its number. If no rank is lower than its number (i.e. there are no gaps in the table) the query returns the max number + 1.
select coalesce(min(number),1) from (
select min(cnt) number
from (
select
number,
(select count(*) from (select distinct number from numbers) b where b.number <= a.number) as cnt
from (select distinct number from numbers) a
) t1 where number > cnt
union
select max(number) + 1 number from numbers
) t1
http://sqlfiddle.com/#!7/720cc/3
Just another method, using EXCEPT this time:
SELECT a + 1 AS missing FROM T
EXCEPT
SELECT a FROM T
ORDER BY missing
LIMIT 1;
In my application I use SELECT TOP 12 * clause to select top 12 records from database and show it to user. In another case I have to show the same result one by one. So I use SELECT TOP 1 * clause,rest of the query is same. I used Sql row_number() function to select items one by on serially.
The problem is SELECT TOP 1 * doesn't return me same row as I get in SELECT TOP 12 *. Also the result set of SELECT TOP 12 * get changed each time I execute the query.
Can anybody explain me why the result is not get same in SELECT TOP 12 * and SELECT TOP 1 *.
FYI: here is my sql
select distinct top 1 * from(
select row_number() over ( ORDER BY Ratings desc ) as Row, * from(
SELECT vw.IsHide, vw.UpdateDate, vw.UserID, vw.UploadPath, vw.MediaUploadID, vw.Ratings, vw.Caption, vw.UserName, vw.BirthYear, vw.BirthDay, vw.BirthMonth, vw.Gender, vw.CityProvince, vw.Approved
FROM VW_Media as vw ,Users as u WITH(NOLOCk)
WHERE vw.IsHide='false' and
GenderNVID=5 and
vw.UserID=u.UserID and
vw.UserID not in(205092) and
vw.UploadTypeNVID=1106 and
vw.IsDeleted='false' and
vw.Approved = 1 and
u.HideProfile=0 and
u.StatusNVID=126 and
vw.UserID not in(Select BlockedToUserID from BlockList WITH(NOLOCk) where UserID=205092) a) totalres where row >0
Thanks in Advance
Sachin
When you use SELECT TOP, you must use also the ORDER BY clause to avoid different results every time.
For performance resons, the database is free to return the records in any order it likes if you don't specify any ordering.
So, you always have to specify in which order you want the records, if you want them in any specific order.
Up to some version of SQL Server (7 IIRC) the natural order of the table was preserved in the result if you didn't specify any ordering, but this feature was removed in later versions.