I need to add a constraint to one table in my database. The table name is Experience. And there is a column named ToDate. Every time the select statement executes like following.
select ToDate from Experience
It should return current date.
So every time select statement executes, the ToDate column get updated with current date.
I know I can do this with some type of sql trigger but is there a way to do it by sql constraint.
like
alter table add constraint...
Any help will be appreciated.
Thanks
You can use a computed column. That's specified like colname as <expression>:
create table t1(id int, dt as getdate());
insert t1 values (1);
select * from t1;
To add contraint ...
create table tbl (id int identity, dt datetime, colval varchar(10))
ALTER TABLE dbo.tbl
ADD CONSTRAINT col_dt_def
DEFAULT GETDATE() FOR dt;
Example of inserting to the table ..
insert into dbo.tbl(colval)
select 'somevalue'
select * from dbo.tbl
The result will be ..
id dt colval
1 2014-08-19 13:31:57.577 somevalue
You cannot use a constraint, because a constraint is basically a rule on what can go in the table, how the table can relate to others, etc. It has no bearing on the data in the table once it goes into the table. Now if I am understanding you correctly, you want to update the ToDate column whenever you select that column. Now you can't use a trigger either as mentioned here and here. They suggest a stored procedure where you would use an update followed by an insert. This is probably my preferred SQL method to go with if you have to use it repeated, which you seem to have to do. Though Andomar's answer is probably better.
Try this link code make help full
http://www.sqlatoms.com/queries/how-to-use-the-getdate-function-in-sql-server-3/
CREATE TABLE ProductOrders
(
OrderId int NOT NULL PRIMARY KEY IDENTITY,
ProductName nvarchar(50) NOT NULL,
OrderDate datetime NOT NULL DEFAULT GETDATE()
)
Related
I have like 11 columns in my database table and i am inserting data in 10 of them. i want to have a unique number like "1101 and so on" in the 11th column.
Any idea what should i do?? Thanks in advance.
SQL Server 2012 and above you can generate Sequence
Create SEQUENCE RandomSeq
start with 1001
increment by 1
Go
Insert into YourTable(Id,col1...)
Select NEXT VALUE FOR RandomSeq,col1....
or else you can use Identity
Identity(seed,increment)
You can start the seed from 1101 and increment the sequence by 1
Create table YourTable
(
id INT IDENTITY(1101,1),
Col varchar(10)
)
If you want to have that unique number in a different field then you can manipulate that field with primary key and insert that value.
If you want in primary key value, then open the table in design mode, go to 'Identity specification', set 'identity increment' and 'identity seed' as you want.
Alternatively you can use table script like,
CREATE TABLE Persons
(
ID int IDENTITY(12,1) PRIMARY KEY,
FName varchar(255) NOT NULL,
)
here the primary key will start seeding from 12 and seed value will be 1.
If you have your table definition already in place you can alter the column and add Computed column marked as persisted as:
ALTER TABLE tablename drop column column11;
ALTER TABLE tablename add column11 as '11'
+right('000000'+cast(ID as varchar(10)), 2) PERSISTED ;
--You can change the right operator value from 2 to any as per the requirements.
--Also replace ID with the identity column in your table.
create table inc
(
id int identity(1100,1),
somec char
)
I have table with 500 records in it and want to insert new column as "serial number" starting with 1.
If you care about the order in which the identity values are assigned, you are best off doing this:
CREATE TABLE dbo.NewTable
(
SerialNumber INT IDENTITY(1,1),
... other columns from original table ...
);
INSERT dbo.NewTable(...other columns...)
SELECT ...other columns...
FROM dbo.OriginalTable
ORDER BY ...ordering criteria...
OPTION (MAXDOP 1); -- to prevent parallelism from messing with identity
DROP TABLE dbo.OriginalTable;
EXEC sp_rename N'dbo.NewTable', N'OriginalTable', N'OBJECT';
You may have to deal with constraints etc. and you will want to do this in a transaction. The point is that just adding an identity column to the table with assign the identity values in an arbitrary order. If you don't care about how the existing values are assigned serial numbers, then just use Kyle's answer.
This could be achieved as follows:
alter table YourTable
add SrNo int identity(1,1)
in PostgreSQL just do:
ALTER TABLE ttaabbllee ADD COLUMN columnName serial NOT NULL; and done!..
I have create a table with
create table tblConsultationHour
(
consultationID int primary key identity,
cday varchar(50),
cstartTime datetime,
cendTime datetime
)
I want to insert value of the day name into cday, and i should know the day name from the cstarttime of date part. what i know on how to get the day name with this code
SELECT DATENAME(dw,'2011-10-26 12:35:29.123')
may i know how can i insert this on the fly ?
or is that possible to insert in this way ?
insert into tblConsultationHour values
(SELECT DATENAME(dw,'2011-10-26 12:35:29.123'),'2011-10-26 12:35', '2011-10-26 14:35')
You were close:
INSERT INTO tblConsultationHour
SELECT DATENAME(dw,'2011-10-26 12:35:29.123'),'2011-10-26 12:35', '2011-10-26 14:35'
Also check out this question for other examples: SQL INSERT from SELECT
Another approach to consider is a computed column:
create table tblConsultationHour
(
consultationID int primary key identity,
cday as DateName(dw,cStarttime),
cstartTime datetime,
cendTime datetime
)
In your example, cDay is a redundant column. As written, if someone changes the cStarttime value, they must also remember to update the cDay field. While it might not occur or be an issue, it is something to keep in mind...
I have a primary key set up to auto increment.
I am doing multiple queries and I need to retrieve that primary key value to use as a foreign key in another table (IsIdentity = TRUE).
Is there any elegant way to get back the primary key value when I do an insert query? Right now I am requerying and getting the highest value in that column which seems really hacky.
Any suggestions?
If you are using SQL Server 2005 or later, you can use the OUTPUT clause.
create table T(
pk int identity primary key,
dat varchar(20)
);
go
insert into T
output inserted.pk
values ('new item');
go
drop table T;
The output can be directed to a table as well as to the client. For example:
create table T(
pk int identity primary key,
dat varchar(20)
);
create table U(
i int identity(1001,1) primary key,
T_pk int not null,
d datetime
);
go
insert into T
output inserted.pk, getdate()
into U(T_pk,d)
values ('new item'), ('newer item');
go
select * from T;
select * from U;
go
drop table T, U;
Beginning with SQL Server 2008, you can use "composable DML" for more possibilities.
insert into YourTable values (...)
get the new PK with scope_identity()
select scope_identity()
INSERT INTO YourTable (1, 2, etc.)
OUTPUT inserted.yourIDcolumn
VALUES (value1, value2, value...)
Note: This is for MS SQL 2005 and greater
SCOPE_IDENTITY() is probably what you want. It returns the ID of the last record inserted by the same code context in which it executes.
IDENT_CURRENT('tablename') is subject to concurrency issues. That is, there's no guarantee that another record won't be inserted between the INSERT and the call to IDENT_CURRENT.
I must confess, I'm not sure to what source of amazement the VillageIdiot's outburst refers, but I myself am quite astonished that this question does not appear to be a duplicate at all.
holy crap!!!
just call SCOPE_IDENTITY() function:
insert into your_talble(col1,col2) values('blah','more blah')
select scope_identity()
because selecting highest value will return error if any other statement make an insert. the function scope_identity() returns the identity created in current context (that is by your statement)
You should use scope_identity(). And I recommend to wrap insert statement and scope_identity() into transaction.
Let's say that I want to have a table that logs the date and the number of columns in some other table (or really any sort of math / string concat etc).
CREATE TABLE `log` (
`id` INTEGER NOT NULL AUTO_INCREMENT ,
`date` DATETIME NOT NULL ,
`count` INTEGER NOT NULL ,
PRIMARY KEY (`id`)
);
Is it possible to have the count column calculated for me whenever I do an insert?
e.g. do something like:
INSERT INTO log (date='foo');
and have count calculated by mysql.
Obviously I could do it myself by doing a query to get the count and inserting it, but this would be better.
Triggers are the best tool for annotating data when a table is changed by insert, update or delete.
To automatically set the date column of a new row in the log with the current date, you'd create a trigger that looked something like this:
create trigger log_date before insert on log
for each row begin
set new.date = current_date()
end;
You definitly have to declare what to insert. This should be possible by using the INSERT ... SELECT statement.
INSERT INTO log (date, count)
SELECT DATE() as date, count(id) as count
from foo;
Which should insert a new row into the log table, containing todays date and the number of rows in the foo table. (Assuming the foo table has an id column.. Use the primary key or another indexed column)
Why don't you use information_schema.TABLES?