I know it works with following code in MySQL to achieve such goal:
set #n = 0;
select (#n := #n + 1),test_score from test_score where student_name = 'Gao' and test_subject = 'math'
In SQLite,there is no variable, so how can I implement similar function in SQLite?
Thanks!
Assuming you have an ID field in your test_score table you could just easily add ORDER BY ID ASC to your select query.
CREATE TABLE test_score (ID INTEGER AUTOINCREMENT, student_name TEXT, test_subject TEXT, score TEXT)
SELECT ID, score FROM test_score WHERE student_name='Gao' AND test_subject='math' ORDER BY ID ASC;
NB: by default the query would be ordered by the ID anyway, but in case you would want to switch it to the most recent just replace ASC with DESC
Related
Need to modify the data in an SQLite database that has fields similar to:
hash (string)
modTime (long, time in ms)
data (any data, e.g. string)
I know the hash value of the record to set the data for (it's really xxHash of some binary blob). There can be several records with the same hash, but I need to modify only the one with MAX(modTime) value with the matching hash... Can't figure out how to construct the UPDATE command.
You can use NOT EXISTS in the WHERE clause:
UPDATE tablename
SET data = new_data
WHERE hash = ?
AND NOT EXISTS (SELECT 1 FROM tablename t WHERE t.hash = tablename.hash AND t.modTime > tablename.modTime)
Or use the column rowid to find the row that you want to update:
UPDATE tablename
SET data = new_data
WHERE rowid = (SELECT rowid FROM tablename WHERE hash = ? ORDER BY modTime DESC LIMIT 1)
or with FIRST_VALUE() window function:
UPDATE tablename
SET data = new_data
WHERE rowid = (SELECT DISTINCT FIRST_VALUE(rowid) OVER (ORDER BY modTime DESC) FROM tablename WHERE hash = ?)
Replace new_data with the new value of data and ? with the value of hash you search for.
I'm trying to replace a placeholder string inside a selection of 10 random records with a random string (a name) taken from another table, using only sqlite statements.
i've done a subquery in order to replace() of the placeholder with the results of a subquery. I thought that each subquery loaded a random name from the names table, but i've found that it's not the case and each placeholder is replaced with the same string.
select id, (replace (snippet, "%NAME%", (select
name from names
where gender = "male"
) )
) as snippet
from imagedata
where timestamp is not NULL
order by random()
limit 10
I was expecting for each row of the SELECT to have different random replacement every time the subquery is invoked.
hello i'm %NAME% and this is my house
This is the car of %NAME%, let me know what you think
instead each row has the same kind of replacement:
hello i'm david and this is my house
This is the car of david, let me know what you think
and so on...
I'm not sure it can be done inside sqlite or if i have to do it in php over two different database queries.
Thanks in advance!
Seems that random() in the subquery is only evaluated once.
Try this:
select
i.id,
replace(i.snippet, '%NAME%', n.name) snippet
from (
select
id,
snippet,
abs(random()) % (select count(*) from names where gender = 'male') + 1 num
from imagedata
where timestamp is not NULL
order by random() limit 10
) i inner join (
select
n.name,
(select count(*) from names where name < n.name and gender = 'male') + 1 num
from names n
where gender = 'male'
) n on n.num = i.num
Example:
It does not work.
UPDATE column_name SET rownum FROM table_name
This work!
UPDATE table_name SET column_name = rownum;
This works but the update is performed incorrectly
SELECT * FROM table_name ORDER BY column_name;
UPDATE table_name SET column_name = rownum;
I wish the following update behavior:
Note:'rownum ' It is not a physical column of the table
/*
pc_comentario = tableName
cod_comentario = columnName (Reference column for sorting)
dtc_andamento = columnDay (Reference column to update the "columnName" according to the order of this column)
*/
rownum | columnName | columnDay
1 1 day 1
2 5 day 5
3 7 day 2
After change with update
rownum | columnName (Update this column) | columnDay (sort by this column)
1 1 day 1
2 2 day 2
3 3 day 5
ALMOST DONE! this column 'cod_comentario_1 "which was materialized in RAM is correct. I need this column" cod_comentario_1 "that does not exist in the table is acknowledged in the consultations with java.
SELECT cod_comentario, dtc_andamento, cod_processo ,
ROW_NUMBER()
OVER (PARTITION BY cod_processo
ORDER BY dtc_andamento) cod_comentario_1
FROM pc_comentario
upadate do not work this way:
UPDATE (
SELECT cod_processo
ROW_NUMBER()
OVER (PARTITION BY cod_processo
ORDER BY dtc_andamento)cod_comentario_1
FROM pc_comentario
) SET cod_comentario_1)
order by Seq
I must enter the values of this consultation in a new column that I created
SELECT
ROW_NUMBER()
OVER (PARTITION BY cod_processo
ORDER BY dtc_andamento DESC)
FROM pc_comentario
Try:
UPDATE table_name
SET column_name = rownum
Shouldn't it be like below rather; I believe UPDATE statement has no FROM clause
UPDATE table_name SET column_name = rownum;
Again, it will work only if rownum is an existing column in your table. If you are trying to use Oracle rownum instead then consider using row_number() function rather
update table_name set column_name =
select rn from ( select column_name, row_number() over (order by column_name) rn
from table_name ) xx;
As you state yourself, rownum is a virtual column. It assigns a sequential value to each row of a particular result set. Which means that the row number of a row could be completely different in the result set of a different query.
If you really want to show the row number as part of the result set, specify it as you would any column:
select rownum as columnName, columnDay
from table
order by ...;
I am trying to assign 'A' to [Student Details].group based on this SELECT statement.
SELECT TOP (10) PERCENT [Person Id], [Given Names], Surname, Gpa, [Location Cd]
FROM [Student Details]
WHERE ([Location Cd] = 'PAR')
ORDER BY Gpa DESC
I can't figure out how to use a SELECT statement in an UPDATE statement.
Can someone please explain how to accomplish this?
I am using ASP .NET and MsSQL Server if it makes a difference.
Thanks
I'm assuming you want to update these records and then return them :
SELECT TOP (10) PERCENT [Person Id], [Given Names], Surname, Gpa, [Location Cd]
INTO #temp
FROM [Student Details]
WHERE ([Location Cd] = 'PAR')
ORDER BY Gpa DESC
update [Student Details] set group='A' where [person id] in(select [person id] from #temp)
select * from #temp
I'm also assuming person id is the PK of student details
Try this using CTE (Common Table Expression):
;WITH CTE AS
(
SELECT TOP 10 PERCENT [Group]
FROM [Student Details]
WHERE ([Location Cd] = 'PAR')
ORDER BY Gpa DESC
)
UPDATE CTE SET [Group] = 'A'
Is this you want?
Update top (10) Percent [Student Details] set [group] = 'A'
where [Location Cd] = 'PAR' AND [group] is null
I have this table
CREATE TABLE APmeasure
(id_APmeasure INTEGER PRIMARY KEY AUTOINCREMENT
, RSSI TEXT, TimeOfMeasure DATETIME
, BSSID TEXT, id_APm INTEGER NOT NULL
, FOREIGN KEY (id_APm) REFERENCES APTable (id_Ap) ON DELETE CASCADE)
I want to make a query which would give me distinct results of TimeOfMeasure and BSSID, like this:
SELECT DISTINCT TimeOfMeasure, BSSID
FROM APmeasure
WHERE "condition"
But that would retrieve me the other columns on the table, related to the DISTINCT query.
How do I do it?
Perform distinct/grouping operation,
Join to result of distinct/grouping operation...
Something like:
SELECT [whichever columns you want]
FROM APmeasure
JOIN (
SELECT TimeOfMeasure, BSSID
FROM APmeasure
WHERE [condition]
GROUP BY TimeOfMeasure, BSSID
) x
ON x.TimeOfMeasure = APmeasure.TimeOfMeasure
AND x.BSSID = APmeasure.BSSID
[any other joins you need]