I want to put some special constraints over my values in the next table:
CREATE TABLE MyTable
{
id varchar(100) NOT NULL PRIMARY KEY,
first_special varchar(8), <- I want it to have max of 8 symbols with no spaces in it
second_special float <- I want it to have precision of 2 decimal points after the '.'
}
EDIT:
The platform is Microsoft SQL Server.
In Oracle (and I think in all dbs) the second one is easy.
second_special NUMBER(5,2) -- The max number would be 999.99
Related
ALTER TABLE table_name ALTER COLUMN column_name [int] (4) NULL;
unable to execute the script, please assist how can I add maximum length to already existed column for an int data type.
If I understand correctly, you want to add a constraint to the column so that it cannot contain a value larger than 9999:
ALTER TABLE table_name
ADD CONSTRAINT CK_column_name_RANGE CHECK (column_name >= 0 AND column_name <= 9999)
SQL Server's integer data types use binary integers. The INT data type is a 32-bit signed number, which allows values from -2^31 (-2,147,483,648) to 2^31-1 (2,147,483,647). You cannot specify the width of such integers, except by choosing TINYINT or SMALLINT.
If you must somehow prevent numbers outside the range that fits in four digits from getting into your table, you can use the DECIMAL data type; it allows you to specify the digit count.
column_name DECIMAL(4,0)
The commission classification column should be able to store integers up to a maximum value of 99 and be named Comm_id. The value of the Comm_id column should be set to a value of 10 automatically if no value is provided when a row is added. The benefits code column should also accommodate integer values up to a maximum of 99 and be named Ben_id.
alter table ACCTMANAGER
add (Comm_id varchar2(99),
Ben_id varchar2(99));
I dont know if this is right
alter table ACCTMANAGER add(Comm_id number(2) default 10, Ben_id number(2));
Basically for number data type you have precision and scale. and if scale is not specified scale is 0 which means no decimal places after the number. number(2) means you can only store up to two digit number here and default keyword set the value automatically if column was not specified.
BTW try using oracle documentation for this homework type of stuff. here is with good examples.
https://docs.oracle.com/cd/B28359_01/server.111/b28318/datatype.htm#i16209
EDITED
alter table ACCTMANAGER add(Comm_id number(2) default 10 constraint lowchk1 check(comm_id>=0) , Ben_id number(2) constraint lowchk2 check(ben_id>=0));
Sorry I can't check syntax for sure as I don't have Oracle installed at home. I only work at it at office.
#MSStp provided a good answer, but you still need constraints to make sure you don't get bad data in the table (such as negative numbers). If the constraint is that the commission and the benefit columns must contain integers between 0 and 99, and you want to make sure Oracle will not accept an input of 2.2 (which it WILL accept in MS's solution, it will just truncate it to 2 and store 2 in the database), you need to add constraints as Abdul Rehman Sayed suggested in a Comment to your question.
alter table acctmanager
add ( comm_id number(2) default 10
constraint check_comm ( comm_id >= 0 and comm_id = trunc(comm_id) ),
ben_id number(2)
constraint check_ben ( ben_id >= 0 and ben_id = trunc(ben_id) )
)
;
However: Just a thought..... What are comm_id and ben_id? If they are some sort of codes to specific commission and benefit descriptions/levels/whatever, do you really need check constraints? Do you have different tables explaining these codes, where comm_id and ben_id are (or should be) primary keys? In which case you need foreign key constraints, NOT check constraints?
ALTER TABLE ACCTMANGER ADD(Comm_id NUMBER(2) DEFAULT 10 NOT NULL, Ben_id NUMBER(2));
After that, you can see that the table is altered.
To see the Output write this:
DESC ACCTMANAGER;
You will see the whole table with the updated column.
I am fairly new to SQL but have been working hard to learn. I am currently stuck on an issue with setting a primary key to have 8 digits no matter what.
I tried using INT(8) but that didn't work. Also AUTO_INCREMENT doesn't work in PostgreSQL but I saw there were a couple of data types that auto increment but I still have the issue of the keys not being long enough.
Basically I want to have numbers represent User IDs, starting at 10000000 and moving up. 00000001 and up would work too, it doesn't matter to me.
I saw an answer that was close to this, but it didn't apply to PostgreSQL unfortunately.
Hopefully my question makes sense, if not I'll try to clarify.
My code (which I am using from a website to try and make my own forum for a practice project) is:
CREATE Table users (
user_id INT(8) NOT NULL AUTO_INCREMENT,
user_name VARCHAR(30) NOT NULL,
user_pass VARCHAR(255) NOT NULL,
user_email VARCHAR(255) NOT NULL,
user_date DATETIME NOT NULL,
user_level INT(8) NOT NULL,
UNIQUE INDEX user_name_unique (user_name),
PRIMARY KEY (user_id)
) TYPE=INNODB;
It doesn't work in PostgreSQL (9.4 Windows x64 version). What do I do?
You are mixing two aspects:
the data type allowing certain values for your PK column
the format you chose for display
AUTO_INCREMENT is a non-standard concept of MySQL, SQL Server uses IDENTITY(1,1), etc.
Use a serial column in Postgres:
CREATE TABLE users (
user_id serial PRIMARY KEY
, ...
)
That's a pseudo-type implemented as integer data type with a column default drawing from an attached SEQUENCE. integer is easily big enough for your case (-2147483648 to +2147483647).
If you really need to enforce numbers with a maximum of 8 decimal digits, add a CHECK constraint:
CONSTRAINT id_max_8_digits CHECK (user_id BETWEEN 0 AND < 99999999)
To display the number in any fashion you desire - 0-padded to 8 digits, for your case, use to_char():
SELECT to_char(user_id, '00000000') AS user_id_8digit
FROM users;
That's very fast. Note that the output is text now, not integer.
SQL Fiddle.
A couple of other things are MySQL-specific in your code:
int(8): use int.
datetime: use timestamp.
TYPE=INNODB: just drop that.
You could make user_id a serial type column and set the seed of this sequence to 10000000.
Why?
int(8) in mysql doesn't actually only store 8 digits, it only displays 8 digits
Postgres supports check constraints. You could use something like this:
create table foo (
bar_id int primary key check ( 9999999 < bar_id and bar_id < 100000000 )
);
If this is for numbering important documents like invoices that shouldn't have gaps, then you shouldn't be using sequences / auto_increment
i am not sure if i could use conditional statement while creating new columns.
Code:
create table Employees(
Emp_ID int primary key identity (1,1),
Hours_worked int,
Rate int default '')
/*Now here in default value i want to set different rates depending upon hours worked. like if hour worked is greater than 8 then rate is 300, if hours worked is less than 8 hour the rate is 200.) How to write this as a Default value in sql server 2008.
My second question is:
Why i get error if i write like this,
create table tbl_1(
col_1 varchar(max) unique
)
The error is
Column 'col_1' in table 'tbl_1' is of a type that is invalid for use as a key column in an index.
Msg 1750, Level 16, State 0, Line 1
Regards
Waqar
you can use COMPUTED Column, http://msdn.microsoft.com/en-us/library/ms191250.aspx
create table Employees(
Emp_ID int primary key identity (1,1),
Hours_worked int,
Rate as (case when Hours_worked > 8 then 300 else 200 end) persisted )
The default value cannot refer to any other column names. So the "default" value of Rate won't know the value of Hours_worked. You could handle it with a trigger or whatever is doing the actual inserting could contain this logic.
http://msdn.microsoft.com/en-us/library/ms173565(v=sql.100).aspx
You cannot but a UNIQUE constraint on a VARCHAR(MAX) field.
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
)