This question is new twist of An IF inside a check constraint SQL. I want to do something similar to the following check (which throws an ORA-00936: missing expression exception):
ALTER TABLE t_table
ADD CONSTRAINT chk_unique_active CHECK
(
( tb_active = 0 ) OR
( tb_active = -1 AND UNIQUE(tb_active, tb_img, tb_objid))
);
The objetive is to be sure (at DBMS level) that only one row with the same objid is active although inactive rows can be duplicated (an historical view of the rows).
It can be done in a trigger but it seems to be better using the check as explained in UNIQUE constraint vs checking before INSERT question.
is this possible?
Do this with a unique index:
create unique index unq_table_active
on ( (case when tb_active = -1 then tb_img end),
(case when tb_active = -1 then tb_objid end)
)
Oracle allows multiple rows with NULL values in a unique index.
Related
I have two tables, TBTC03 and TBTC03Y, with TBTC03Y having two extra columns as EFFDTE and EXPDTE. I have to merge the data from TBTC03 to TBTC03Y with the following logic:
If no matching TC03 entry is found in TC03Y
a new TC03Y record is build with the TC03 data
the Effective Date will default to '01-01-1980'
the Expiration Date will default to '09-30-1995'
I wrote a query for the same as :
insert into TBTC03Y (LOB,MAJPERIL,LOSSCAUSE,NUMERICCL,EFFDTE,EXPDTE)
select LOB,MAJPERIL,LOSSCAUSE,NUMERICCL,'0800101' ,'0950930'
from TBTC03 where not EXISTS (select * from TBTC03Y where
TBTC03Y.LOB = TBTC03.LOB AND
TBTC03Y.MAJPERIL = TBTC03.MAJPERIL AND
TBTC03Y.LOSSCAUSE = TBTC03.LOSSCAUSE AND
TBTC03Y.NUMERICCL = TBTC03.NUMERICCL)
The primary key for both the tables is LOB, MAJPERIL and LOSSCAUSE.
However i have some TBTC03Y records, that already have the data with the primary key.
Firing the above query gives primary key constraints on some of the rows.
I am unable to figure out how i can acomplish it.
The issue with the primary key is that you're also including NUMERICCL in the WHERE clause. If you remove this you'll then be inserting unique data.
You may have to create a separate process as it appears you have some records in each table that have the same LOB, MAJPERIL and LOSSCAUSE but have a different NUMERICCL. I can think of three options here;
You have an issue with the data that needs fixing.
Maybe you want to update this value to match, in which case you're looking at an UPDATE rather than INSERT INTO.
You need to update your composite primary key to include the column NUMERICCL.
Removing NUMERICCL from the where clause would also correct this.
If the PK for both tables is {LOB, MAJPERIL, LOSSCAUSE}, you should remove TBTC03Y.NUMERICCL = TBTC03.NUMERICCL from your where clause.
Example:
t1{LOB, MAJPERIL, LOSSCAUSE, NUMERICCL}
1 1 1 1
t2{LOB, MAJPERIL, LOSSCAUSE, NUMERICCL}
1 1 1 2
In t2 there is no row where:
TBTC03Y.LOB = TBTC03.LOB AND
TBTC03Y.MAJPERIL = TBTC03.MAJPERIL AND
TBTC03Y.LOSSCAUSE = TBTC03.LOSSCAUSE AND
TBTC03Y.NUMERICCL = TBTC03.NUMERICCL
But inserting will obvioulsy violate PK constraint in t2:
t2{LOB, MAJPERIL, LOSSCAUSE}
1 1 1
In a database application, I want to insert, update and delete records in a table of database.
Table is as below:
In this table, Ga1_ID is Primary Key.
Suppose, I insert 5 records as show currently.
In second attempt, if I want to insert 5 other records and if any of these new records contains a primary key attribute which is already present in table it show error. Its fine.
But, when I insert new 5 records... how I can verify these new records's primary key value is not present. I mean, how to match or calculate the already present primary key attributes and then insert new records.
What is the best approach to manage this sort of situation ?
use following query in dataadapter:
da=new SqlDataAdapter("select Ga1_ID from table where Ga1_ID=#pkVal",conn);
DataSet=new DataSet();
da.fill(ds);
//pass parameter for #pkVal
da.SelectCommand.Parameters(1).Value = pkValue;
if(ds.Tables[0].Rows.Count>0) //If number of rows >0 then record exists
BEGIN
messagebox.show("Primary key present");
END
Hope its helpful.
Do not check existing records in advance, i.e. do not SELECT and then INSERT. A better (and pretty common) approach is to try to INSERT and handle exceptions, in particular, catch a primary key violation if any and handle it.
Do the insert in a try/catch block, with different handling in case of a primary key violation exception and other sql exception types.
If there was no exception, then job's done, record was inserted.
If you caught a primary key violation exception, then handle it appropriately (your post does not specify what you want to do in this case, and it's completely up to you)
If you want to perform 5 inserts at once and want to make sure they all succeed or else roll back if any of them failed, then do the inserts within a transaction.
you can do a lookup first before inserting.
IF EXISTS (SELECT * FROM tableName WHERE GA1_id=#newId)
BEGIN
UPDATE tableName SET Ga1_docid = #newdocID, GA1_fieldNAme = #newName, Ga1_fieldValue = #newVal where GA1_id=#newId
END
ELSE
BEGIN
INSERT INTO tableName(GA1_ID, Ga1_docid, GA1_fieldNAme Ga1_fieldValue) VALUES (value1,val2,value3,value4)
END
If you're using SQL Server 2012, use a sequence object - CREATE SEQUENCE.
This way you can get the next value using NEXT VALUE FOR.
With an older SQL Server version, you need to create the primary key field as an IDENTITY field and use the SCOPE_IDENTITY function to get the last identity value and then increment it manually.
Normally, you would like to have a surrogate key wich is generally an identity column that will automatically increment when you are inserting rows so that you don't have to care about knowing which id already exists.
However, if you have to manually insert the id there's a few alternatives for that and knowing wich SQL database you are using would help, but in most SQL implementations, you should be able to do something like:
IF NOT EXISTS
IF NOT EXISTS(
SELECT 1
FROM your_table
WHERE Ga1_ID = 1
)
INSERT INTO ...
SELECT WHERE NOT EXISTS
INSERT INTO your_table (col_1, col_2)
SELECT col_1, col_2
FROM (
SELECT 1 AS col_1, 2 AS col_2
UNION ALL
SELECT 3, 4
) q
WHERE NOT EXISTS (
SELECT 1
FROM your_table
WHERE col_1 = q.col_1
)
For MS SQL Server, you can also look at the MERGE statement and for MySQL, you can use the INSERT IGNORE statement.
I'm trying to formulate some check constraints in SQL Anywhere 9.0.
Basically I have schema like this:
CREATE TABLE limits (
id INT IDENTITY PRIMARY KEY,
count INT NOT NULL
);
CREATE TABLE sum (
user INT,
limit INT,
my_number INT NOT NULL CHECK(my_number > 0),
PRIMARY KEY (user, limit)
);
I'm trying to force a constraint my_number for each limit to be at most count in table.
I've tried
CHECK ((SELECT sum(my_number) FROM sum WHERE limit = limit) <= (SELECT count FROM limits WHERE id = limit))
and
CHECK (((SELECT sum(my_number) FROM sum WHERE limit = limit) + my_number) <= (SELECT count FROM limits WHERE id = limit))
and they both seem not to do the correct thing. They are both off by one (meaning once you get a negative number, then insertion will fail, but not before that.
So my question is, with what version of the table are these subqueries being executed against? Is it the table before the insertion happens, or does the subquery check for consistency after the insert happens, and rolls back if it finds it invalid?
I do not really understand what you try to enforce here but based on this help topic.
Using CHECK constraints on columns
Once a CHECK condition is in place, future values are evaluated
against the condition before a row is modified.
I would go for a before insert trigger. You have more options and can bring up a better error message.
Let's say that I have a table of items, and for each item, there can be additional information stored for it, which goes into a second table. The additional information is referenced by a FK in the first table, which can be NULL (if the item doesn't have additional info).
TABLE item (
...
item_addtl_info_id INTEGER
)
CONSTRAINT fk_item_addtl_info FOREIGN KEY (item_addtl_info)
REFERENCES addtl_info (addtl_info_id)
TABLE addtl_info (
addtl_info_id INTEGER NOT NULL
GENERATED BY DEFAULT
AS IDENTITY (
INCREMENT BY 1
NO CACHE
),
addtl_info_text VARCHAR(100)
...
CONSTRAINT pk_addtl_info PRIMARY KEY (addtl_info_id)
)
What is the "best practice" to update an item's additional info (in IBM DB2 SQL, preferably)?
It should be an UPSERT operation, meaning that if additional info does not yet exist then a new record is created in the second table, but if it does, then it is only updated, and the FK in the first table does not change.
So imperatively, this is the logic:
UPSERT(item, item_info):
CASE WHEN item.item_addtl_info_id IS NULL THEN
INSERT INTO addtl_info (item_info)
UPDATE item.item_addtl_info_id (addtl_info.addtl_info_id)
^^^^^^^^^^^^^
ELSE
UPDATE addtl_info (item_info)
END
My main problem is how to get the newly inserted addtl_info row's id (underlined above). In a stored proc I can request the id from a sequence and store it in a variable, but maybe there is a more straightforward way. Isn't it something that comes up all the time when programming databases?
I mean, I'm really not interested in what the id of the addtl_info record is as long as it remains unique and is referenced properly. So using sequences seems a bit of an overkill to me in this case.
As a matter of fact, this UPSERT operation should be part of the SQL language as a standard operation (maybe it is, and I just don't know about it?)...
The syntax I was looking for is:
SELECT * FROM NEW TABLE ( INSERT INTO phone_book VALUES ( 'Peter Doe','555-2323' ) )
from Wikipedia (http://en.wikipedia.org/wiki/Insert_%28SQL%29)
This is how to refer to the record that was just inserted in the table.
My colleague called this construct an "in-place trigger", which what it really is...
Here is the first version that I put together as a compound SQL statement:
begin atomic
declare addtl_id integer;
set addtl_id = (select item_addtl_info_id from item where item.item_id = XXX);
if addtl_id is null
then
set addtl_id = (select addtl_info_id from new table
(insert into addtl_info
(addtl_info_text)
values ('My brand new additional info')
)
);
update item set item.item_addtl_info_id = addtl_id
where item.item_id = XXX;
else
update addtl_info set addtl_info_text = 'My updated additional info'
where addtl_info.addtl_info_id = addtl_id;
end if;
end
XXX being equal to the item id to be updated - this code can now be easily inserted into a sproc, and XXX can be converted to an input parameter.
I also tried using MERGE INTO, but I couldn't figure out a syntax for updating a table different from what was specified as the target.
There is a need to build constraint on the column that guarantees that only one value in all rows is 1 and all the others are 0.
Solution with triggers exists but I would like to have something built in.
Is such thing possible at all?
Edit
Actually I just noticed you are on SQL Server 2008 you could use a filtered index for this
CREATE UNIQUE NONCLUSTERED INDEX UIX ON YourTable (col) where col = 1
Original Answer
The easiest way would probably be to store this one special pk in a separate one row table. The no more than one row aspect can be enforced with check constraints.
CREATE TABLE OneRowTable
(
lock CHAR(1) DEFAULT 'X' NOT NULL PRIMARY KEY CHECK (lock = 'X'),
OtherTablePK int
);
Otherwise assuming you might have an id field comprised of positive integers you could add a computed column with the following definition
case when col=1 then -1 else id end
and add a unique constraint to that.