For a test tomorrow we're told to name our constraints
I know it's possible to create a constraint when you use ALTER TABLE
but can you add a name to a not null constraint when you CREATE TABLE?
f.e.
CREATE TABLE test (
test1 VARCHAR
CONSTRAINT nn_test1 NOT NULL (test1)
)
I get an error when trying to run this query. Am I writing it wrong?
The error I get is
ERROR: syntax error at or near "NOT"
LINE 3: CONSTRAINT nn_test1 NOT NULL (test1))
^
SQL state: 42601
Character: 56
You have two options to define a named not null constraint:
Inline with the column:
CREATE TABLE test
(
test1 VARCHAR CONSTRAINT nn_test1 NOT NULL,
test2 integer --<< no comma because it's the last column
);
Or at the end of columns as an out-of-line constraint. But then you need a check constraint:
CREATE TABLE test
(
test1 VARCHAR,
test2 integer, --<< comma required after the last column
constraint nn_test1 check (test1 is not null)
);
This has become irrelevant, since you're not using SQL Server
First of all, you should always specify a length for a VARCHAR. Not doing so (in SQL Server variables, or parameters) may result in a string of just exactly ONE character in length - typically NOT what you want.
Then, you need to just specify the NOT NULL - there's no need to repeat the column name (actually this is the error) - if you're specifying the CONSTRAINT "inline" with the column definition (which is a perfectly legal and in my opinion the preferred way of doing this).
Try this code:
CREATE TABLE test
(
test1 VARCHAR(50)
CONSTRAINT nn_test1 NOT NULL
)
At least this is the CREATE TABLE statement that works in T-SQL / SQL Server - not sure about PostgreSQL (don't know it well enough, don't have it at hand to test right now).
I, a_horse_with_no_name, the two syntax:
constraint nn_test1 check (test1 is not null)
and
test1 VARCHAR CONSTRAINT nn_test1 NOT NULL
are equivalent ? performance correctly ecc.
Because in first case the SQL server exception return the name nn_test so the system know exactly error.
Related
How can I add a not null constraint to a table with 'or' operator? I want either the personal OR work phone number to be present for each entry.
I am trying this:
ALTER TABLE user_data MODIFY ( personal_number NOT NULL || work_number NOT NULL);
but get this error:
ORA-00907: missing right parenthesis
You need a check constraint that checks each column:
ALTER TABLE user_data
ADD CONSTRAINT check_numbers
CHECK ( personal_number IS NOT NULL AND work_number IS NULL ) OR
( personal_number IS NULL AND work_number IS NOT NULL )
)
Note this disallows having both present though. Which may or may not be your business rule. But I think you have enough now to tweak that if you need to.
To check that at least one of personal and work number is present, you can use the OR operator in a CHECK constraint:
ALTER TABLE user_data
ADD CONSTRAINT personal_or_work_number_required__chk
CHECK ( personal_number IS NOT NULL OR work_number IS NOT NULL);
fiddle
Note: The || operator is for string concatenation and is not the logical OR operator.
Table definition:
CREATE TABLE IF NOT EXISTS public.test
(
"Id" integer NOT NULL GENERATED ALWAYS AS IDENTITY (INCREMENT 1 START 1 MINVALUE 1 MAXVALUE 2147483647 CACHE 1),
"SomeColumn" character(100) COLLATE pg_catalog."default",
CONSTRAINT test_pkey PRIMARY KEY ("Id")
)
TABLESPACE pg_default;
ALTER TABLE IF EXISTS public.test
OWNER to postgres;
I am trying this query:
INSERT INTO public.test VALUES ('testData');
But PostgreSQL throws this error:
ERROR: invalid input syntax for type integer: "testData"
LINE 1: INSERT INTO public.test VALUES ('testData');
I know this is valid in SQL Server. Is there a way the achieve this behaviour in PostgreSQL?
I do not want to specify the column names. Columns are defined in the order, but the identity column does not exist in the query.
I want to not give the column names
That's a bad idea. You should always specify the target columns for an INSERT statement. Especially if you want to skip some, but not others.
However, if you insist on bad coding style, you can use the DEFAULT keyword
INSERT INTO public.test VALUES (DEFAULT, 'testData');
I want to ensure that only the values 'Expert', 'Average' or 'Adequate' are entered into the levelOfExpertise column of this table, however whenever I do try an enter one of those values, it returns an error saying the value entered is too short. Here is the create table query for this particular table. The the column I am referring to is levelOfExpertise:
CREATE TABLE MusicianInstrument
(
musicianNo varchar(5) not null
CONSTRAINT MI_PK1 REFERENCES Musician(musicianNo),
instrumentName varchar(50) not null
CONSTRAINT MI_PK2 REFERENCES Instrument(instrumentName),
levelOfExpertise varchar(50),
CONSTRAINT levelOfExpertise CHECK (levelOfExpertise = 'Expert', 'Adequate', 'Avergage'),
PRIMARY KEY(musicianNo,instrumentName)
);
Any ideas how I can ensure only those three values (Expert, Adequate or Average) can be entered?
Thanks
Use the IN operator
CHECK (levelOfExpertise IN ('Expert','Adequate','Avergage'))
Try to change your CHECK constraint as following:
CONSTRAINT levelOfExpertise CHECK (levelOfExpertise IN ('Expert','Adequate','Avergage'))
I suppose that you use sql server as RDBMS.
I have set-up a table using the following SQL script:
CREATE TABLE MY_TABLE (
ID NUMBER NOT NULL,
CODE VARCHAR2(40) NOT NULL,
CONSTRAINT MY_TABLE PRIMARY KEY (ID)
);
CREATE UNIQUE INDEX XUNIQUE_MY_TABLE_CODE ON MY_TABLE (CODE);
The problem is that I need to ensure that CODE does not have a leading zero for its value.
How do I accomplish this in SQL so that a 40-char value without a leading zero is stored?
CODE VARCHAR2 NOT NULL CHECK (VALUE not like '0%')
sorry - slight misread on the original spec
If you can guarantee that all INSERTs and UPDATEs to this table are done through a stored procedure, you could put some code there to check that the data is valid and return an error if not.
P.S. A CHECK CONSTRAINT would be better, except that MySQL doesn't support them.
I use SQL Server 2008
I use a CHECK CONSTRAINT on multiple columns in the same table to try to validate data input.
I receive an error:
Column CHECK constraint for column
'AAAA' references another column,
table 'XXXX'.
CHECK CONSTRAINT does not work in this way.
Any other way to implement this on a single table without using FK?
Thanks
Here an example of my code
CREATE TABLE dbo.Test
(
EffectiveStartDate dateTime2(2) NOT NULL,
EffectiveEndDate dateTime2(2) NOT NULL
CONSTRAINT CK_CmsSponsoredContents_EffectiveEndDate CHECK (EffectiveEndDate > EffectiveStartDate),
);
Yes, define the CHECK CONSTRAINT at the table level
CREATE TABLE foo (
bar int NOT NULL,
fred varchar(50) NOT NULL,
CONSTRAINT CK_foo_stuff CHECK (bar = 1 AND fred ='fish')
)
You are declaring it inline as a column constraint
...
fred varchar(50) NOT NULL CONSTRAINT CK_foo_fred CHECK (...)
...
Edit, easier to post than describe. Fixed your commas.
CREATE TABLE dbo.Test
(
EffectiveStartDate dateTime2(2) NOT NULL,
EffectiveEndDate dateTime2(2) NOT NULL, --need comma
CONSTRAINT CK_CmsSponsoredContents_EffectiveEndDate CHECK (EffectiveEndDate > EffectiveStartDate) --no comma
);
Of course, the question remains are you using a CHECK constraint where it should be an FK constraint...?
Check constraints can refer to a single column or to the whole record.
Use this syntax for record-level constraints:
ALTER TABLE MyTable
ADD CONSTRAINT MyCheck
CHECK (...your check expression...)
You can simply apply your validation in a trigger on the table especially that either way the operation will be rolled back if the check failed.
I found it more useful for CONSTRAINT using case statements.
ALTER TABLE dbo.ProductStock
ADD
CONSTRAINT CHK_Cost_Sales
CHECK ( CASE WHEN (IS_NOT_FOR_SALE=0 and SAL_CPU <= SAL_PRICE) THEN 1
WHEN (IS_NOT_FOR_SALE=1 ) THEN 1 ELSE 0 END =1 )