I want to use prisma on an existing database. Now that I'm researching it, I realise that all my tables and columns are incorrectly named. I would like to correct the names, but I don't want to lose my data.
I did a prisma "pull" so I have a schema of my current database. But then I don't quite understand how (if possible) do I rename my tables and columns using the schema.
What are my options? Can I change the schema.prisma and make prisma take care of all the "alter" statements? How do I do this?
It's not natively supported yet. There is a Feature Request to handle renames effectively.
You can use this technique to rename your tables and fields without dropping the data.
Create an empty migration file with prisma migrate dev --create-only
Add sql: ALTER TABLE IF EXISTS "OldName" RENAME TO "NewName";
Change table name in schema.prisma file
Run prisma migrate dev
Related
I am about to model a PostgreSQL database, based on an Oracle database. The latter is old and its tables have been named after a 3-letter-scheme.
E.g. a table that holds parameters for tasks would be named TSK_PAR.
As I model the new database, I'd like to rename those tables to a more descriptive name using actual words. My problem is, that some parts of the software might rely on these old names until they're rewritten and adapted to the new scheme.
Is it possible to create something like an alias that's being used for the whole database?
E.g. I create a new task_parameters database, but add a TSK_PAR alias to it, so if a SELECT * FROM TSK_PAR is being used, it automatically refers to the new name?
Postgres has no synonyms like Oracle.
But for your intended use case, views should do just fine. A view that simply does select * from taks_parameters is automatically updateable (see here for an online example).
If you don't want to clutter your default schema (usually public) with all those views, you can create them in a different schema, and then adjust the user's search path to include that "synonym schema".
For example:
create schema synonyms;
create table public.task_parameters (
id integer primary key,
....
);
create view synonyms.task_par
as
select *
from public.task_parameters;
However, that approach has one annoying drawback: if a table is used by a view, the allowed DDL statements on it are limited, e.g. you can't drop a column or rename it.
As we manage our schema migrations using Liquibase, we always drop all views before applying "normal" migrations, then once everything is done, we simply re-create all views (by running the SQL scripts stored in Git). With that approach, ALTER TABLE statements never fail because there are not views using the tables. As creating a view is really quick, it doesn't add overhead when deploying a migration.
We have many postgresql databases with the same structure using only public shcema on each one.
How can I group all of them in a single database using separate schemas?
You can dump the database definition and data out, edit the output by putting the default schema as whatever you choose and run the scripts back into database.
Remember to make the dump in SQL format, pg_dump with default custom format won't work. The schema change will only need a change on a row like
SET search_path TO *whateverschema*
If you don't want to edit the dumps (maybe they're very large), you can of course also restore them one by one to the public schema, alter the tables into the desired schema and then repeat for the next one.
There is no special way to convert an existing database into a schema in another database unfortunately.
I forgot to post the answer afer all klin comment was the answer, this step was the solution,
Inside customer_x database:
alter schema public rename to customer_x;
And then take pg_dump customer_x:
pg_dump "customer_x" --schema "customer_x" -f customer_x.sql
Inside new conglomerated database:
DROP schema customer_x CASCADE;
create schema customer_x;
Then load the dump of customer_x:
psql "conglomerated_database" -f customer_x.sql
I am trying to rename a table in db2 like so
rename table schema1.mytable to schema2.mytable
but getting the following error message:
the name "mytable" has the wrong number of qualifiers.. SQLCODE=-108,SQLSTATE=42601
what is the problem here.... I am using the exact syntax from IBM publib documentation.
You cannot change the schema of a given object. You have to recreate it.
There are severals ways to do that:
If you have only one table, you can export and import/load the table. If you use the IDX format, the DDL will be included in the generated file. If using another format, the table has be created.
You can recreate the table by using:
Create table schema2.mytable like schema1.mytable
You can extract the DDL with the db2look tool
If you are changing the schema name for a schema given, you can use ADMIN_COPY_SCHEMA
These last two options only create the table structure, and you still need to import the data. After having create the table, you insert the data by different ways:
Inserting directly
insert into schema2.mytable select * from schema1.mytable
Via load from cursor
Via a Load or import from file (The file exported in the previous step)
The problem is the foreign relations, because they have to be recreated.
Finally, you can create an alias. It is easier, and you do not have to deal with relations.
You can easily rename a table with this statement:
RENAME TABLE SCHEMA.TABLENAME TO NEWTABLENAME;
You're not renaming table in provided example, you're trying to move to different schema, it's not the same thing. Look into db2move tool for this.
if you want to rename a table in the same schema, you can use like this.
RENAME TABLE schema.table_name TO "new_table_name";
Otherwise, you can use tools like DBeaver to rename or copy tables in a db2 db.
What if you leave it as is and create an alias with the new name and schema.
Renaming a table means to rename a table within same schema .To rename in other schema ,db2 call its ALIAS:
db2 create alias for
In my case, i have backup file in full database. Now I want to restore some particulars tables in public schema.
Those tables are already stored in another schema. Any Feasible solution is there? and How to do it
It's not clear whether the tables you want to restore were backed up from the schema "public", or whether they were backed up from a different schema.
If your backup is in archive format, not in a plain text format, you can restore individual tables (see the -n and -t options to pg_restore). As far as I know, you can't restore them to a different schema. Instead, you'd restore them to their original schema, then move each table with ALTER TABLE table_name SET SCHEMA new_schema;.
Since you already have tables of the same name in the target schema, I expect you'll have to rename them before restoring from backup. After you restore from backup, and you move the restored tables to the schema "public", you can rename those tables to their original names. PostgreSQL understands that public.table_name and new_schema.table_name are different tables.
I am using Eclipse, Java and a Derby database. I want to experiment with changing values that rewrite one of the tables in the db. Before starting the change I would like to copy the particular table (not in code) so that I can restore the original data if necessary. Sof ar googling and searching this site hasnt produced an answer. In Eclipse there is an option to export the db but it calls it a connection so I am not usre what would happen.
If you're not sure about how to connect to the database and issue sql statements, you will need to learn about JDBC. This is a good place to start.
If you're asking about the SQL, it's pretty straight forward. You can create a table based on a select statement.
e.g.
create table table2 as select * from table1 with no data;
Derby is a little strange in this area. You must specify the with no data, and the created table will be empty. You can then issue an insert that will populate the new table if you wish.
insert into table2 select * from table1;
The new table will not have indexes. You will need to create them if you want them. It might retain the primary key. You should check that if you're testing against it. If it doesn't retain the primary key, you should create the primary key before inserting data into the table.
In Eclipse there is an option to export the db but it calls it a connection so I am not sure what would happen.
If what Eclipse does isn't clear for you, you can just as well zip your entire database directory (content of DERBY_HOME env. variable) into an archive. The database must not be running while you make the backup.