In MySQL, what I did is:
update table set group = 1 where log(id) < 0
I wanna do same thing in R but I have no idea
What should I do?
We can use data.table in R. Convert the 'data.frame' to 'data.table' (setDT(tab)), using the logical condition in 'i', we assign (:=) 1 to 'group' variable. As this does in place, it would be much faster and efficient.
library(data.table)
setDT(tab)[log(id) <0, group := 1]
Using sqldf: You cannot use group as the variable name so im changing to catg.
sqldf(c("update table set catg = 1 where log(id) < 0", "select * from main.xy"))
Related
I have two variables i have declared and asigned values to, I want to pass them to an sql query limits in python. Below is what i have tried so far. Any help will be very much appreciated
limitstart = 10
limitend = 100
df = pd.read_sql("SELECT NUMBERS FROM `table` LIMIT '{limitstart}', '{limitend}'", con=dbConnection)
I am getting a syntax error. I would want the query to eventually be
df = pd.read_sql("SELECT NUMBERS FROM `table` LIMIT 10, 100", con=dbConnection)
But i need to pass the variables
You have to just make a string of command so try something like
df = pd.read_sql("SELECT NUMBERS FROM table LIMIT " + str(limitstart) + ", "+str(limitend),con = dbConnection)
For Python3 you're missing f before your query and have unnecessary ':
limitstart = 10
limitend = 100
df = pd.read_sql(f"SELECT NUMBERS FROM `table` LIMIT {limitstart}, {limitend}", con=dbConnection)
I have a SQL query. But that contains a where condition, and the OR in that where is not working.
Query
SELECT `st_student`.`st_id`, `ab_date`, `as_date` `st_status`
FROM (`st_student`)
WHERE `st_status` = 1
OR `st_status` = 2
AND `ab_date` BETWEEN '08/01/2015' AND '08/31/2015'
OR `as_date` BETWEEN '08/01/2015' AND '08/31/2015'
AND `aca_no` = 2
GROUP BY `st_student`.`st_id`
This condition is not working:
OR `as_date` BETWEEN '08/01/2015' AND '08/31/2015'
Is there any mistake in that?
One possible error concerns the use of the AND and OR operators, since AND has priority over OR, and your query can be interpreted in the wrong way. So you should use the parentheses, and write something like this:
SELECT `st_student`.`st_id`, `ab_date`, `as_date` `st_status`
FROM `st_student`
WHERE (`st_status` = 1 OR `st_status` = 2)
AND (`ab_date` BETWEEN '08/01/2015' AND '08/31/2015'
OR `as_date` BETWEEN '08/01/2015' AND '08/31/2015')
AND `aca_no` = 2
GROUP BY `st_student`.`st_id`
In case that your columns are declared as a varchar datatype you will need to use str_to_date function. Varchar cannot be compared as a date unless you convert it to one. Try this and let me know. Best of luck.
SELECT `st_student`.`st_id`, `ab_date`, `as_date` `st_status`
FROM `st_student`
WHERE (`st_status` = 1 OR `st_status` = 2)
AND STR_TO_DATE(`ab_date`,'%d/%m/%Y')
BETWEEN
STR_TO_DATE('01/08/2015','%d/%m/%Y')
AND
STR_TO_DATE('31/08/2015','%d/%m/%Y')
OR
STR_TO_DATE(`as_date`,'%d/%m/%Y')
BETWEEN
STR_TO_DATE('01/08/2015','%d/%m/%Y')
AND
STR_TO_DATE('31/08/2015','%d/%m/%Y')
AND `aca_no` = 2
GROUP BY `st_student`.`st_id`
I'm spinning in circles trying to figure out what is likely a very simple SQL structure. My task seems simple - within the same table I need to update 3 related records with data from one master record. The master coordinates are in the record with a class of 'T', and I want to insert that record's coordinates into the rx_latitude/longitude columns of the related records with class code 'R'
The table structure is: callsign, class, tx_latitude, tx_longitude, rx_latitude, rx_longitude. Sample data looks like this:
J877, T, 40.01, -75.01, 0, 0
J877, R, 39.51, -75.21, 0, 0
J877, R, 40.25, -75.41, 0, 0
J877, R, 39.77, -75.61, 0, 0
Within that same table, I want to populate all of the rx_latitude and rx_longitude fields where the class is 'R' with the tx_latitude and tx_longitude coordinates where the class is 'T' and the callsign matches.
I've tried several insert and update statements, but I can only seem to operate on the master record, not the related records. I would appreciate any guidance that you might offer.
You can use UPDATE...FROM statement:
UPDATE theTable
SET
tx_latitude = masterRecord.tx_latitude,
tx_longitude = masterRecord.tx_longitude
FROM
(SELECT tx_latitude,tx_longitude,callsign FROM theTable WHERE class='T') masterRecord
WHERE
class='R' AND callsign = masterRecord.callsign
Updated
Try :
update yourTable t1, yourTable t2 set
t1.tx_latitude = t2.tx_latitude,
t1.tx_longitude = t2.tx_longitude
where t1.class = 'R' and t2.class = 'T' and t1.callsign = t2.callsign
Example
You can use MySQL's update ... join syntax.
It would go something like this:
update yourtable toUpdate
left join yourtable masterRecordTable
on toUpdate.callsign = masterRecordTable.callsign and masterRecordTable.class = 'T'
set toUpdate.rx_latitude = masterRecordTable.tx_latitude,
toUpdate.rx_longitude = masterRecordTable.tx_longitude
where toUpdate.callsign = 'J877' and toUpdate.class = 'R'
See this fiddle for a working example
Presently troubleshooting a problem where running this SQL query:
UPDATE tblBenchmarkData
SET OriginalValue = DataValue, OriginalUnitID = DataUnitID,
DataValue = CAST(DataValue AS float) * 1.335
WHERE
FieldDataSetID = '6956beeb-a1e7-47f2-96db-0044746ad6d5'
AND ZEGCodeID IN
(SELECT ZEGCodeID FROM tblZEGCode
WHERE(ZEGCode = 'C004') OR
(LEFT(ZEGParentCode, 4) = 'C004'))
Results in the following error:
Msg 8114, Level 16, State 5, Line 1
Error converting data type nvarchar to float.
The really odd thing is, if I change the UPDATE to SELECT to inspect the values that are retrieved are numerical values:
SELECT DataValue
FROM tblBenchmarkData
WHERE FieldDataSetID = '6956beeb-a1e7-47f2-96db-0044746ad6d5'
AND ZEGCodeID IN
(SELECT ZEGCodeID
FROM tblZEGCode WHERE(ZEGCode = 'C004') OR
(LEFT(ZEGParentCode, 4) = 'C004'))
Here are the results:
DataValue
2285260
1205310
Would like to use TRY_PARSE or something like that; however, we are running on SQL Server 2008 rather than SQL Server 2012. Does anyone have any suggestions? TIA.
It would be helpful to see the schema definition of tblBenchmarkData, but you could try using ISNUMERIC in your query. Something like:
SET DataValue = CASE WHEN ISNUMERIC(DataValue)=1 THEN CAST(DataValue AS float) * 1.335
ELSE 0 END
Order of execution not always matches one's expectations.
If you set a where clause, it generally does not mean the calculations in the select list will only be applied to the rows that match that where. SQL Server may easily decide to do a bulk calculation and then filter out unwanted rows.
That said, you can easily write try_parse yourself:
create function dbo.try_parse(#v nvarchar(30))
returns float
with schemabinding, returns null on null input
as
begin
if isnumeric(#v) = 1
return cast(#v as float);
return null;
end;
So starting with your update query that's giving an error (please forgive me for rewriting it for my own clarity):
UPDATE B
SET
OriginalValue = DataValue,
OriginalUnitID = DataUnitID,
DataValue = CAST(DataValue AS float) * 1.335
FROM
dbo.tblBenchmarkData B
INNER JOIN dbo.tblZEGCode Z
ON B.ZEGCodeID = Z.ZEGCodeID
WHERE
B.FieldDataSetID = '6956beeb-a1e7-47f2-96db-0044746ad6d5'
AND (
Z.ZEGCode = 'C004' OR
Z.ZEGParentCode LIKE 'C004%'
)
I think you'll find that a SELECT statement with exactly the same expressions will give the same error:
SELECT
OriginalValue,
DataValue NewOriginalValue,
OriginalUnitID,
DataUnitID OriginalUnitID,
DataValue,
CAST(DataValue AS float) * 1.335 NewDataValue
FROM
dbo.tblBenchmarkData B
INNER JOIN dbo.tblZEGCode Z
ON B.ZEGCodeID = Z.ZEGCodeID
WHERE
B.FieldDataSetID = '6956beeb-a1e7-47f2-96db-0044746ad6d5'
AND (
Z.ZEGCode = 'C004' OR
Z.ZEGParentCode LIKE 'C004%'
)
This should show you the rows that can't convert:
SELECT
B.*
FROM
dbo.tblBenchmarkData B
INNER JOIN dbo.tblZEGCode Z
ON B.ZEGCodeID = Z.ZEGCodeID
WHERE
B.FieldDataSetID = '6956beeb-a1e7-47f2-96db-0044746ad6d5'
AND (
Z.ZEGCode = 'C004' OR
Z.ZEGParentCode LIKE 'C004%'
)
AND IsNumeric(DataValue) = 0
-- AND IsNumeric(DataValue + 'E0') = 0 -- try this if the prior doesn't work
The trick in the last commented line is to tack on things to the string to force only valid numbers to be numeric. For example, if you wanted only integers, IsNumeric(DataValue + '.0E0') = 0 would show you those that aren't.
How do I do this
Select top 10 Foo from MyTable
in Linq to SQL?
Use the Take method:
var foo = (from t in MyTable
select t.Foo).Take(10);
In VB LINQ has a take expression:
Dim foo = From t in MyTable _
Take 10 _
Select t.Foo
From the documentation:
Take<TSource> enumerates source and yields elements until count elements have been yielded or source contains no more elements. If count exceeds the number of elements in source, all elements of source are returned.
In VB:
from m in MyTable
take 10
select m.Foo
This assumes that MyTable implements IQueryable. You may have to access that through a DataContext or some other provider.
It also assumes that Foo is a column in MyTable that gets mapped to a property name.
See http://blogs.msdn.com/vbteam/archive/2008/01/08/converting-sql-to-linq-part-7-union-top-subqueries-bill-horst.aspx for more detail.
Use the Take(int n) method:
var q = query.Take(10);
The OP actually mentioned offset as well, so for ex. if you'd like to get the items from 30 to 60, you would do:
var foo = (From t In MyTable
Select t.Foo).Skip(30).Take(30);
Use the "Skip" method for offset.
Use the "Take" method for limit.
#Janei: my first comment here is about your sample ;)
I think if you do like this, you want to take 4, then applying the sort on these 4.
var dados = from d in dc.tbl_News.Take(4)
orderby d.idNews descending
select new
{
d.idNews,
d.titleNews,
d.textNews,
d.dateNews,
d.imgNewsThumb
};
Different than sorting whole tbl_News by idNews descending and then taking 4
var dados = (from d in dc.tbl_News
orderby d.idNews descending
select new
{
d.idNews,
d.titleNews,
d.textNews,
d.dateNews,
d.imgNewsThumb
}).Take(4);
no ? results may be different.
This works well in C#
var q = from m in MyTable.Take(10)
select m.Foo
Whether the take happens on the client or in the db depends on where you apply the take operator. If you apply it before you enumerate the query (i.e. before you use it in a foreach or convert it to a collection) the take will result in the "top n" SQL operator being sent to the db. You can see this if you run SQL profiler. If you apply the take after enumerating the query it will happen on the client, as LINQ will have had to retrieve the data from the database for you to enumerate through it
I do like this:
var dados = from d in dc.tbl_News.Take(4)
orderby d.idNews descending
select new
{
d.idNews,
d.titleNews,
d.textNews,
d.dateNews,
d.imgNewsThumb
};
You would use the Take(N) method.
Taking data of DataBase without sorting is the same as random take
Array oList = ((from m in dc.Reviews
join n in dc.Users on m.authorID equals n.userID
orderby m.createdDate descending
where m.foodID == _id
select new
{
authorID = m.authorID,
createdDate = m.createdDate,
review = m.review1,
author = n.username,
profileImgUrl = n.profileImgUrl
}).Take(2)).ToArray();
I had to use Take(n) method, then transform to list, Worked like a charm:
var listTest = (from x in table1
join y in table2
on x.field1 equals y.field1
orderby x.id descending
select new tempList()
{
field1 = y.field1,
active = x.active
}).Take(10).ToList();
This way it worked for me:
var noticias = from n in db.Noticias.Take(6)
where n.Atv == 1
orderby n.DatHorLan descending
select n;