Can't ALTER TABLE in ACCESS 2012 - sql

I'm trying to alter the table of an access database. I keep getting a syntax error for something I think should be pretty simple.
Here is what I tried to do and the error I am getting.


yes you have syntax error as what access tells you, try this one
ALTER TABLE EMP_2 ADD COLUMN EMP_PCT NUMBER(4);
ALTER TABLE EMP_2 ADD COLUMN PROJ_NUM CHAR(3);
the syntax
ALTER TABLE table {ADD {COLUMN field type[(size)] [NOT NULL] [CONSTRAINT index] |
ALTER COLUMN field type[(size)] |
CONSTRAINT multifieldindex} |
DROP {COLUMN field I CONSTRAINT indexname}}
ALTER TABLE statement

Related

Error in changing column length in Postgres

I am trying to change the column size from 100 to 150 varchar data type using following query:
alter table data_warehouse.tbl_abc
alter column first_nm varchar(150) null;
Getting the following error:
SQL Error [42601]: ERROR: syntax error at or near "varchar"
Position: 77

The syntax is a bit different, so try this:
ALTER TABLE data_warehouse.tbl_abc
ALTER COLUMN first_nm type varchar(120);

The error in your syntax is that you missed a TYPE keyword:
ALTER TABLE data_warehouse.tbl_abc
ALTER COLUMN first_nm TYPE varchar(150);
and if you have a NOT NULL constraint you want to remove, add a new ALTER COLUMN inside the same ALTER TABLE statement:
ALTER TABLE data_warehouse.tbl_abc
ALTER COLUMN first_nm TYPE varchar(150),
ALTER COLUMN first_nm DROP NOT NULL;
for reference look here: https://www.postgresql.org/docs/current/sql-altertable.html
Edit: as in the comment, if you have a view which involves the same column, drop it and re-create it under transaction:
BEGIN TRANSACTION;
DROP VIEW [...];
ALTER TABLE [...];
CREATE VIEW [...];
COMMIT;
Be aware that to alter a table, you must acquire an exclusive lock on it, so during the whole process, all the queries over the same table and on the views of the table are locked, also if they don't read from the altered column (because the whole table is locked) - use with caution in production environment

DB2: How do I remove AUTO_INCREMENT?

How do I remove AUTO_INCREMENT of a column in DB2?
I tried
ALTER TABLE my_table ALTER my_id
but no luck. What is the correct SQL statement?

You can modify a column definition of a DB2 table and remove the generation of values:
ALTER TABLE mytable ALTER COLUMN mycol DROP GENERATED;

You can remove the Auto_increment by using the following
ALTER TABLE table_name ALTER COLUMN column_name DROP IDENTITY;

Change length of column of table which have dependencies

I've got a table named Contacts with column Title varchar(50) . Now in the middle of development I want to change the length to varchar(100) of field Title .At the moment table Contacts has over 25 dependencies (other tables, views functions).
When I run following sql statement in sql server 2008 . I am getting errors.
ALTER TABLE [Contacts ] ALTER COLUMN [Title ] varchar(100)
Error Like
Msg 5074, Level 16, State 1, Line 2
The object 'Contacts_title' is dependent on column 'title'.
And more.

you have to drop are recreate the constrains on the Contact table to do that or (sometime not really recommended ) you can temporary disable the constrain, alter the length and enable them again
--disable all constraints for the Sales.SalesOrderHeader table
ALTER TABLE [yourtable] NOCHECK CONSTRAINT ALL
--do your stuff
--do something --enable all constraints for the Sales.SalesOrderHeader table
ALTER TABLE [yourtable] CHECK CONSTRAINT ALL

You have to remove the dependence, and then create it again.

MS Access - sql expression for allow null?

I use MS Access (2003) database. Once I create a column I set NOT NULL using sql statement:
ALTER TABLE Table1
ALTER column myColumn INTEGER not null
Is there a way to change it back to allow null values? I already tried:
ALTER TABLE Table1
ALTER column myColumn INTEGER null
but nothing...

You cant specify null in ALTER TABLE (although not null is allowed)
See the below documentation and also this discussion on this toppic
Syntax
ALTER TABLE table {ADD {COLUMN field type[(size)] [NOT NULL] [CONSTRAINT index] | ALTER COLUMN field type[(size)] | CONSTRAINT multifieldindex} | DROP {COLUMN field I CONSTRAINT indexname} }
Old School Solution:-
create a new temporray field as null with the same datatype
update the new temporary field to the existing NOT NULL field
drop the old NOT NULL field
create the droped column with the same datatype again without NOT NULL
update the existing field to the temporary field
if there have been indices on the existing field, recreate these
drop the temporary field

Try something like this using MODIFY :-
ALTER TABLE Table1 MODIFY myColumn INT NULL;

The only way I've found is to use DAO directly on the table.
Set db.TableDefs(strTable1).Fields(strFieldName).Required = false

Altering a column to be nullable

I want to alter a table column to be nullable. I have used:
ALTER TABLE Merchant_Pending_Functions Modify NumberOfLocations NULL
This gives an error at Modify. What is the correct syntax?

Assuming SQL Server (based on your previous questions):
ALTER TABLE Merchant_Pending_Functions ALTER COLUMN NumberOfLocations INT NULL
Replace INT with your actual datatype.

If this was MySQL syntax, the type would have been missing, as some other responses point out.
Correct MySQL syntax would have been:
ALTER TABLE Merchant_Pending_Functions MODIFY NumberOfLocations INT NULL
Posting here for clarity to MySQL users.

In PostgresQL it is:
ALTER TABLE tableName ALTER COLUMN columnName DROP NOT NULL;

for Oracle Database 10g users:
alter table mytable modify(mycolumn null);
You get "ORA-01735: invalid ALTER TABLE option" when you try otherwise
ALTER TABLE mytable ALTER COLUMN mycolumn DROP NOT NULL;

Although I don't know what RDBMS you are using, you probably need to give the whole column specification, not just say that you now want it to be nullable. For example, if it's currently INT NOT NULL, you should issue ALTER TABLE Merchant_Pending_Functions Modify NumberOfLocations INT.

As others have observed, the precise syntax for the command varies across different flavours of DBMS. The syntax you use works in Oracle:
SQL> desc MACAddresses
Name Null? Type
----------------------------------------- -------- ----------------------------
COMPUTER NUMBER
MACADDRESS VARCHAR2(12)
CORRECTED_MACADDRESS NOT NULL VARCHAR2(17)
SQL> alter table MACAddresses
2 modify corrected_MACAddress null
3 /
Table altered.
SQL> desc MACAddresses
Name Null? Type
----------------------------------------- -------- ----------------------------
COMPUTER NUMBER
MACADDRESS VARCHAR2(12)
CORRECTED_MACADDRESS VARCHAR2(17)
SQL>

For SQL Server or TSQL
ALTER TABLE Complaint.HelplineReturn ALTER COLUMN IsDisposed BIT NULL

This depends on what SQL Engine you are using, in Sybase your command works fine:
ALTER TABLE Merchant_Pending_Functions
Modify NumberOfLocations NULL;

For HSQLDB:
ALTER TABLE tableName ALTER COLUMN columnName SET NULL;

ALTER TABLE Merchant_Pending_Functions MODIFY COLUMN `NumberOfLocations` INT null;
This will work for you.
If you want to change a not null column to allow null, no need to include not null clause. Because default columns get not null.
ALTER TABLE Merchant_Pending_Functions MODIFY COLUMN `NumberOfLocations` INT;

Oracle
ALTER TABLE Merchant_Pending_Functions MODIFY([column] NOT NULL);

SQLite
The ALTER TABLE command is a bit special. There is no possibility to modify a column. You have to create a new column, migrate the data, and then drop the column:
-- 1. First rename
ALTER TABLE
Merchant_Pending_Functions
RENAME COLUMN
NumberOfLocations
TO
NumberOfLocations_old
-- 2. Create new column
ALTER TABLE
Merchant_Pending_Functions
ADD COLUMN
NumberOfLocations INT NULL
-- 3. Migrate data - you need to write code for that
-- 4. Drop the old column
ALTER TABLE
Merchant_Pending_Functions
DROP COLUMN
NumberOfLocations_old

Make sure you add the data_type of the column to modify.
ALTER TABLE TABLE_NAME MODIFY COLUMN_NAME DATA_TYPE NULL;