This is a small part of the data in my table PLANT I'm having in database...
id name code
123 OFFICE1 A1234
456 OFFICE2 B4567
789 OFFICE3 C8989
When I get all the data from an api, before inserting them into the database, I want to check if any records are present already.
This is how I'm checking if a record is present..
let isExists = sharedInstance.plantExists(thePlantObject, id: 123)
func plantExists(_ items: plant,id: Int) -> Bool {
var isExists = false
sharedInstance.database!.open()
isExists = sharedInstance.database!.executeUpdate("EXISTS(SELECT * FROM PLANT WHERE PLANT.id = ?)", withArgumentsIn: [id])
sharedInstance.database!.close()
return isExists
}
But if I print isExists, then this message is printed... (Bool) isExists = <variable not available>
What am I doing wrong here..?
If you can change the schema of db then make sure id attribute is set as unique and insertion will fail if you are inserting id which already exists in the column.
Or Just do select query with id and see if any results come back to you
Select * from where id =
As per comment #Joakim Danielson, EXISTS should be a part of WHERE clause.
You can achieve it feature two way
1. The way you are approaching (checking existence and based on that insert).
Instead of using EXISTS use following query
SELECT COUNT(id) FROM PLANT WHERE PLANT.id = ?
This way you can get the count of specific id. Here i assume that you didn't put any UNIQUE constraints in id column. If you set UNIQUE constraint in id column, then second approach is the best approach for you.
2. Let the SQLite handle itself (based on a constraint)
While create the db schema, make the id unique. Assumed schema creation query is following
CREATE TABLE plant (
id INT(11) UNIQUE NOT NULL,
name VARCHAR(255)
);
use following query while inserting
INSERT OR IGNORE (`id`, `name`) VALUES (?, ?)
This way, it will ignore inserting if any sort of constraint fails.
Working demo is here.
NB: It won't report any failure.
I have a table that already has values in it. The value I want to update is g_fuel_prft.billed_qty. I need to multiple a number from this table times a number from another table to get the value.
So table names are inv_header which contains inv_header.rpt_factor and g_fuel_prft which contains g_fuel_prft.billed_qty. The criteria is where inv_header.link=g_fuel_prft.lnk AND inv_header.rpt_factor = 0.
once I have those rows selected I want to update them to billed_qty * rpt_factor
update g_fuel_prft
set billed_qty = (inv_header.rpt_factor * g_fuel_prft.billed_qty)
where exists
(select billed_qty,ivh_rpt_factor from g_fuel_prft,inv_header
where g_fuel_prft.prodlnk = inv_header.ivh_link
and inv_header.ivh_rpt_factor = 0)
I am getting an 201 syntax error
You can't refer to inv_header.rpt_factor like that. You'll need to place it into a sub-query.
UPDATE g_fuel_prft
SET billed_qty = ((SELECT inv_header.rpt_factor
FROM inv_header
WHERE g_fuel_prft.prodlnk = inv_header.ivh_link) *
g_fuel_prft.billed_qty)
WHERE EXISTS (SELECT *
FROM g_fuel_prft
JOIN inv_header ON g_fuel_prft.prodlnk = inv_header.ivh_link
WHERE inv_header.ivh_rpt_factor = 0)
With an EXISTS query, the select-list doesn't matter and * is conventional. You might need more restrictions in the sub-select within the SET clause. It depends on what sort of relationship there is between the joining columns (1:1, 1:N, N:1, M:N).
Given the minimal schema below, the query above is syntactically valid. It's hard to test it without valid sample data.
DROP TABLE IF EXISTS g_fuel_prft;
CREATE TABLE g_fuel_prft
(
prodlnk INTEGER NOT NULL,
billed_qty DECIMAL(8,2) NOT NULL
);
DROP TABLE IF EXISTS inv_header;
CREATE TABLE inv_header
(
rpt_factor DECIMAL(8,4) NOT NULL,
ivh_link INTEGER NOT NULL,
ivh_rpt_factor DECIMAL(8,4) NOT NULL
);
I'm trying to convert the following SQL statement to Core Data:
delete from SomeTable
where someID not in (
select someID
from SomeTable
group by property1, property2, property3
)
Basically, I want to retrieve and delete possible duplicates in a table where a record is deemed a duplicate if property1, property2 and property3 are equal to another record.
How can I do that?
PS: As the title says, I'm trying to convert the above SQL statement into iOS Core Data methods, not trying to improve, correct or comment on the above SQL, that is beyond the point.
Thank you.
It sounds like you are asking for SQL to accomplish your objective. Your starting query won't do what you describe, and most databases wouldn't accept it at all on account of the aggregate subquery attempting to select a column that is not a function of the groups.
UPDATE
I had initially thought the request was to delete all members of each group containing dupes, and wrote code accordingly. Having reinterpreted the original SQL as MySQL would do, it seems the objective is to retain exactly one element for each combination of (property1, property2, property3). I guess that makes more sense anyway. Here is a standard way to do that:
delete from SomeTable st1
where someID not in (
select min(st2.someId)
from SomeTable st2
group by property1, property2, property3
)
That's distinguished from the original by use of the min() aggregate function to choose a specific one of the someId values to retain from each group. This should work, too:
delete from SomeTable st1
where someID in (
select st3.someId
from SomeTable st2
join SomeTable st3
on st2.property1 = st3.property1
and st2.property2 = st3.property2
and st2.property3 = st3.property3
where st2.someId < st3.someId
)
These two queries will retain the same rows. I like the second better, even though it's longer, because the NOT IN operator is kinda nasty for choosing a small number of elements from a large set. If you anticipate having enough rows to be concerned about scaling, though, then you should try both, and perhaps look into optimizations (for example, an index on (property1, property2, property3)) and other alternatives.
As for writing it in terms of Core Data calls, however, I don't think you exactly can. Core Data does support grouping, so you could write Core Data calls that perform the subquery in the first alternative and return you the entity objects or their IDs, grouped as described. You could then iterate over the groups, skip the first element of each, and call Core Data deletion methods for all the rest. The details are out of scope for the SO format.
I have to say, though, that doing such a job in Core Data is going to be far more costly than doing it directly in the database, both in time and in required memory. Doing it directly in the database is not friendly to an ORM framework such as Core Data, however. This sort of thing is one of the tradeoffs you've chosen by going with an ORM framework.
I'd recommend that you try to avoid the need to do this at all. Define a unique index on SomeTable(property1, property2, property3) and do whatever you need to do to avoid trying to creating duplicates or to gracefully recover from a (failed) attempt to do so.
DELETE SomeTable
FROM SomeTable
LEFT OUTER JOIN (
SELECT MIN(RowId) as RowId, property1, property2, property3
FROM SomeTable
GROUP BY property1, property2, property3
) as KeepRows ON
SomeTable.RowId = KeepRows.RowId
WHERE
KeepRows.RowId IS NULL
A few pointers for doing this in iOS: Before iOS 9 the only way to delete objects is individually, ie you will need to iterate through an array of duplicates and delete each one. (If you are targeting iOS9, there is a new NSBatchDeleteRequest which will help delete them all in one go - it does act directly on the store but also does some cleanup to eg. ensure relationships are updated where necessary).
The other problem is identifying the duplicates. You can configure a fetch to group its results (see the propertiesToGroupBy of NSFetchRequest), but you will have to specify NSDictionaryResultType (so the results are NOT the objects themselves, just the values from the relevant properties.) Furthermore, CoreData will not let you fetch properties (other than aggregates) that are not specified in the GROUP BY. So the suggestion (in the other answer) to use min(someId) will be necessary. (To fetch an expression such as this, you will need to use an NSExpression, embed it in an NSExpressionDescription and pass the latter in propertiesToFetch of the fetch request).
The end result will be an array of dictionaries, each holding the someId value of your prime records (ie the ones you don't want to delete), from which you have then got to work out the duplicates. There are various ways, but none will be very efficient.
So as the other answer says, duplicates are better avoided in the first place. On that front, note that iOS 9 allows you to specify attributes that you would like to be unique (individually or collectively).
Let me know if you would like me to elaborate on any of the above.
Group-wise Maximum:
select t1.someId
from SomeTable t1
left outer join SomeTable t2
on t1.property1 = t2.property1
and t1.property2 = t2.property2
and t1.property3 = t2.property3
and t1.someId < t2.someId
where t2.someId is null;
So, this could be the answer
delete SomeTable
where someId not in
(select t1.someId
from SomeTable t1
left outer join SomeTable t2
on t1.property1 = t2.property1
and t1.property2 = t2.property2
and t1.property3 = t2.property3
and t1.someId < t2.someId
where t2.someId is null);
Sqlfiddle demo
You can use exists function to check for each row if there is another row that exists whose id is not equal to the current row and all other properties that define the duplicate criteria of each row are equal to all the properties of the current row.
delete from something
where
id in (SELECT
sm.id
FROM
sometable sm
where
exists( select
1
from
sometable sm2
where
sm.prop1 = sm2.prop1
and sm.prop2 = sm2.prop2
and sm.prop3 = sm2.prop3
and sm.id != sm2.id)
);
I think you could easily handle this by creating a derived duplicate_flg column and set it to 1 when all three property values are equal. Once that is done, you could just delete those records where duplicate_flg = 1. Here is a sample query on how to do this:
--retrieve all records that has same property values (property1,property2 and property3)
SELECT *
FROM (
SELECT someid
,property1
,property2
,property3
,CASE
WHEN property1 = property2
AND property1 = property3
THEN 1
ELSE 0
END AS duplicate_flg
FROM SomeTable
) q1
WHERE q1.duplicate_flg = 1;
Here is a sample delete statement:
DELETE
FROM something
WHERE someid IN (
SELECT someid
FROM (
SELECT someid
,property1
,property2
,property3
,CASE
WHEN property1 = property2
AND property1 = property3
THEN 1
ELSE 0
END AS duplicate_flg
FROM SomeTable
) q1
WHERE q1.duplicate_flg = 1
);
Simply, if you want to remove duplicate from table you can execute below Query :
delete from SomeTable
where rowid not in (
select max(rowid)
from SomeTable
group by property1, property2, property3
)
if you want to delete all duplicate records try the below code
WITH tblTemp as
(
SELECT ROW_NUMBER() Over(PARTITION BY Property1,Property2,Property3 ORDER BY Property1) As RowNumber,* FROM Table_1
)
DELETE FROM tblTemp where RowNumber >1
Hope it helps
Use the below query to delete the duplicate data from that table
delete from SomeTable where someID not in
(select Min(someID) from SomeTable
group by property1+property2+property3)
I'm searching a way to simulate "create table as select" in Firebird from SP.
We are using this statement frequently in another product, because it is very easy for make lesser, indexable sets, and provide very fast results in server side.
create temp table a select * from xxx where ...
create indexes on a ...
create temp table b select * from xxx where ...
create indexes on b ...
select * from a
union
select * from b
Or to avoid the three or more levels in subqueries.
select *
from a where id in (select id
from b
where ... and id in (select id from c where))
The "create table as select" is very good cos it's provide correct field types and names so I don't need to predefine them.
I can simulate "create table as" in Firebird with Delphi as:
Make select with no rows, get the table field types, convert them to create table SQL, run it, and make "insert into temp table " + selectsql with rows (without order by).
It's ok.
But can I create same thing in a common stored procedure which gets a select sql, and creates a new temp table with the result?
So: can I get query result's field types to I can create field creator SQL from them?
I'm just asking if is there a way or not (then I MUST specify the columns).
Executing DDL inside stored procedure is not supported by Firebird. You could do it using EXECUTE STATEMENT but it is not recommended (see the warning in the end of "No data returned" topic).
One way to do have your "temporary sets" would be to use (transaction-level) Global Temporary Table. Create the GTT as part of the database, with correct datatypes but without constraints (those would probably get into way when you fill only some columns, not all) - then each transaction only sees it's own version of the table and data...
I have 14 fields which are similar and I search the string 'A' on each of them. I would like after that order by "position" field
-- some set in order to remove a lot of useless text
def col='col01'
select '&col' "Fieldname",
&col "value",
position
from oneTable
where &col like '%A%'
/
-- then for the second field, I only have to type two lines
def col='col02'
/
...
def col='col14'
/
Write all the fields which contains 'A'. The problem is that those field are not ordered by position.
If I use UNION between table, I cannot take advantage of the substitution variables (&col), and I have to write a bash in unix in order to make the replacement back into ksh. The problem is of course that database code have to be hard-coded in this script (connection is not easy stuff).
If I use a REFCURSOR with OPEN, I cannot group the results sets together. I have only one request and cannot make an UNION of then. (print refcursor1 union refcursor2; print refcursor1+refcursor2 raise an exception, select * from refcursor1 union select * from refcursor2, does not work also).
How can concatenate results into one big "REFCURSOR"? Or use a union between two distinct run ('/') of my request, something like holding the request while typing new definition of variables?
Thank you for any advice.
Does this answer your question ?
CREATE TABLE #containingAValueTable
(
FieldName VARCHAR(10),
FieldValue VARCHAR(1000),
position int
)
def col='col01'
INSERT INTO #containingAValueTable
(
FieldName , FieldValue, position
)
SELECT '&col' "Fieldname",
&col "value",
position
FROM yourTable
WHERE &col LIKE '%A%'
/
-- then for the second field, I only have to type two lines
def col='col02'
INSERT INTO...
/
def col='col14'
/
select * from #containingAValueTable order by postion
DROP #containingAValueTable
But I'm not totally sure about your use of the 'substitution variable' called "col" (and i only have SQL Server to test my request so I used explicit field names)
edit : Sorry for the '#' charcater, we use it so often in SQL Server for temporaries, I didn't even know it was SQL Server specific (moreover I think it's mandatory in sql server for creating temporary table). Whatever, I'm happy I could be useful to you.