I have a table1 created in the prod environment. I have to add column to an existing table1.
Im using the function create of replace to create the table with the suitable ddl.
To add the column shall i add it manually on the prod machine and change the ddl.
Or changing only the ddl will do it?
Thank you
As far as i know there is no such thing as a create or replace table syntax. that should only work for functions or views.
Use the ALTER TABLE Table1 ADD NewColumn {DATA_TYPE} command.
The way you phrased your question makes me think you use a 3rd party database version control like liquibase. If that is the case leave the initial create DDL alone and just add it as a separate change. If you change the initial ddl it will only affect new databases.
Related
I have created a table using a 'AS SELECT' statement.
CREATE TABLE TEST AS
SELECT ...
from (MANY TABLES)
WHERE (MANY CONDITIONS);
How do I make sure that updates on any of the table columns go onto TEST as well?
Or do I have to use a VIEW? (which I dont want to as there is a need of a trigger to be working on TEST)
Are any other options available other than using a VIEW ?
You need to create a View.
CREATE TABLE AS SELECT just make a copy of data at the moment of execution.
Look into creating the table test as a materialized view.
Triggers can be placed on these and there are various update options too.
Depending on your database system you could use a Trigger to insert the values in the other table as well. That's if you need something like near-realtime syncronization. Or you might go for a daily/weekly/... batch synchronization.
As I am not so familiar with Oracle you should look at their documentation for a detailed description.
I know you can go into the design view of a table in SQL Server Management Studios and reorder columns as they appear in the design view, however this isn't possible with SQL Azure as the option is disabled. Is there a way to modify SQL Azure tables so that you can reorder their columns as they appear in the design view?
I have been running a number of database upgrades over the last few months to support new requirements and would like to reorder the way the columns appear in design view so they're easier to read, i.e. so they start with a primary key, followed by foreign keys, then normal columns and end with the added by, modified by fields. Its purely to make the tables more readable as I manage them over time.
Just run a script against the table. Its a bit of pseudocode but you should get the idea.
CREATE TABLE TableWithDesiredOrder(PK,FK1,FK2,COL1,COL2)
INSERT INTO TableWithDesiredOrder(PK,FK1,FK2,COL1,COL2....)
SELECT PK,FK1,FK2,COL1,COL2.... FROM OriginalTable
DROP TABLE OriginalTable
Finally Rename the table
sp_Rename TableWithDesiredOrder, OriginalTable
Just another option: I use SQL Delta to propagate my db changes from dev db up to Azure db. So in this case, I just change the col order locally using SSMS GUI, and SQL Delta will do the createnew>copytonew>dropold for me, along with my other local changes. (In Project Options, I set Preserve Column Order=Yes.)
I experienced the same with Azure SQL Database, basically my view changes with ALTER were not taken when did a SELECT * from the view, or the column headers were mixed with the column values.
In order to fix it I dropped the view and re-created it again. That worked.
sometimes i face the following case in my database design,, i wanna to know what is the best practice to handle this case:::
for example i have a specific table and after a while ,, when the database in operation and some real data are already entered.. i need to add some required fields (that supposed not to accept null)..
what is the best practice in this situation..
make the field accept null as (some data already entered in the table ,, and scarify the important constraint )and try to force the user to enter this field through some validation in the code..
truncate all the entered data and reentered them again (tedious work)..
any other suggestions about this issue...
It depends on requirements. If the data to populate existing rows for the new column isn't available immediately then I would generally prefer to create a new table and just populate new rows when the data exists. If and when you have all the data for every row then put the new column into the original table.
If possible i would set a default value for the new column.
e.g. For Varchar
alter table table_name
add column_name varchar(10) not null
constraint column_name_default default ('Test')
After you have updated you could then drop the default
alter table table_name
drop constraint column_name_default
A lot will come down to your requirements.
It depends on your application, your database scheme, your entities.
The best way to go about it is to truncate the data and re - enter it again, but it need not be too tedious an item. Temporary tables and table variables could assist a great deal with this issue. A simple procedure comes to mind to go about it:
In SQL Server Management Studio, Right - click on the table you wish to modify and select Script Table As > CREATE To > New Query Editor Window.
Add a # in front of the table name in the CREATE statement.
Move all records into the temporary table, using something to the effect of:
INSERT INTO #temp SELECT * FROM original
Then run the script to keep all your records into the temporary table.
Truncate your original table, and make any changes necessary.
Right - click on the table and select Script Table As > INSERT To > Clipboard, paste it into your query editor window and modify it to read records from the temporary table, using INSERT .. SELECT.
That's it. Admittedly not quite straightforward, but a well - kept database is almost always worth a slight hassle.
Is it possible to copy a table (with definition, constraints, identity) to a new table?
Generate a CREATE script based on the table
Modify the script to create a different table name
Perform an INSERT from selecting everything from the source table
No, not really, you have to script it out, then change the names
you can do this
select * into NewTable
FROM OldTable
WHERE 1 =2 --if you only want the table without data
but it won't copy any constraints
It's not the most elegant solution, but you could use a tool like the free Database Publishing Wizard from Microsoft.
It creates an SQL script of the table definition including data and including indexes and stuff. But you would have to alter the script manually to change the table name...
Another possibility:
I just found this old answer on SO.
This script is an example to script the constraints of all tables, but you can easily change it to select only the constraints of "your" table.
So, you could do the following:
Create the new table with data like SQLMenace said (select * into NewTable from OldTable)
Add constraints, indexes and stuff by changing this SQL script
Is it possible to create more than one table at a time using single create table statement.
For MySQL, you can use multi-query to execute multiple SQL statements in a single call. You'd issue two CREATE TABLE statements separated by a semicolon.
But each CREATE TABLE statement individually can create only one table. The syntax supported by MySQL does not allow multiple tables to be created simultaneously.
#bsdfish suggests using transactions, but DDL statements like CREATE TABLE cause implicit transaction commits. There's no way to execute multiple CREATE TABLE statements in a single transaction in MySQL.
I'm also curious why you would need to create two tables simultaneously. The only idea I could come up with is if the two tables have cyclical dependencies, i.e. they reference each other with foreign keys. The solution to that is to create the first table without that foreign key, then create the second table, then add the foreign key to the first table with ALTER TABLE ADD CONSTRAINT. Dropping either table requires a similar process in reverse.
Not with MS SQL Server. Not sure about mysql.
Can you give more info on why you'd want to do this? Perhaps there's an alternative approach.
I don't know, but I don't think you can do that. Why you want to do this?
Not in standard SQL using just the 'CREATE TABLE' statement. However, you can write multiple statements inside a CREATE SCHEMA statement, and some of those statements can be CREATE TABLE statements. Next question - does your DBMS support CREATE SCHEMA? And does it have any untoward side-effects?
Judging from the MySQL manual pages, it does support CREATE SCHEMA as a synonym for CREATE DATABASE. That would be an example of one of the 'untoward side-effects' I was referring to.
(Did you know that standard SQL does not provide a 'CREATE DATABASE' statement?)
I don't think it's possible to create more than one table with a 'CREATE TABLE' command. Everything really depends on what you want to do. If you want the creation to be atomic, transactions are probably the way to go. If you create all your tables inside a transaction, it will act as a single create statement from the perspective of anything going on outside the transaction.