Actually the problem arises since we have named a column authorization which is ok on MySQL but fails miserably on Postgres, authorization is a reserved keyword there.
We want to have all schemas in sync even on different databases, so we want to rename authorization in the MySQL catalogue(s) to something neutral.
It would be great if the renaming of the MySQL table columns would work seamlessly with older and newer versions of the applicatation at least for a couple of days so that the transition is smooth.
Does anybody know how to do this? A nice idea would be to have some sort of alias/redirection, e.g. create a new column _authorization that is actually the same column as authorization but under the new name. Queries using the new name _autorization will work as well as queries using the old name. Then we can update the application. If all servers have the latest binaries, we can drop the alias and rename the column.
Any ideas? Any help is greatly appreciated.
A nice idea would be to have some sort of alias/redirection...
No such functionality exists. The closest is to use a view based on the table, because it's easier to rename a column in a view as there isn't any underlying data to change. Otherwise:
Rename the column in MySQL using the ALTER TABLE statement:
ALTER TABLE [your table]
CHANGE authorization [new_col_name] [column_definition]
I also had to use an alias to a column (e.g. a particular app needed 'id' column instead of 'entry_id').
i was able to create a view (MySQL 5.1+ recommended for views) from the table with an extra alias to the culprit column. for the 'authorization' column from your example:
CREATE VIEW maintable_view AS
SELECT *, authorization AS authcol FROM MAINTABLE
if you run a update-query on the view, and set 'authcol' to a new value,
this will update the 'authorization' column in 'maintable'.
UPDATE maintable_view SET authcol=22 WHERE id=3
http://dev.mysql.com/doc/refman/5.1/en/create-view.html
Related
In MS Access, I have a few tables with some column names having spaces in their column names (e.g. Transaction I).
I need to replace the spaces with underscores (e.g. Transaction_ID) using SQL.
Although I'm somewhat familiar with SQL, however, my exposure was in an Oracle environment and all of those queries and functions don't work in MS Access. I am fairly new to MS Access.
I have tried following codes from the posts that I searched, however, to no avail.
alter table EP sp_rename 'Transaction ID' to Transaction_ID
alter table EP rename column 'Transaction ID' to Transaction_ID
Access does not have a built in command "line" option to re-name a column.
(and your example looks to be for SQL Server, and MORE so it looks to be using a library stored procedure function to do this for you. So, that looks to be SQL Server syntax - not MS Access.
If you going to use DDL in Access to re-name a column? You have to create a new column with the desired name, and then move the data to this new column, and then drop the old column.
The so called sql 'ddl' commands in Access actually do quite much follow the SQL standard.
So, before embarking on this road, I would consider to use the built in GUI + table designer. (It will do the dirty work behind the scenes for you).
So, can you use DDL to rename a column? Yes, but you have to do this in 3 steps.
Create the new column.
Copy data from old column to new column
Delete the old column.
Because of indexing, possible relationships and other issues, then one REALLY does want to use the built in table designer + the GUI here.
But, you can use say a procedure (VBA) in Access to do this:
Say we had a REALLY bad column name for City called [The City].
To re-name to City, then we can go:
Sub MyAlter()
' create the new column
CurrentDb.Execute "ALTER TABLE tblHotels ADD COLUMN City TEXT(50)", dbFailOnError
' copy the data
CurrentDb.Execute "UPDATE tblHotels SET City = [The City]", dbFailOnError
' drop the origonal column
CurrentDb.Execute "ALTER TABLE tblHotels DROP COLUMN [The City]", dbFailOnError
End Sub
Just keep in mind that ANY column in Access with spaces (yuk!!) needs to be surrounded with []. This applies to SQL select queries, update queries, insert queries, and of course DDL commands to modify the table structure.
If a one-time deal, then of course simply use access, open the table(s) in question in design mode, and make the changes.
However, if you do for some reason do need to use a procedure, then the above code in a access code module can be used.
Or you could just fire up the query builder, flip to SQL view mode, and type in the above raw sql that way.
(you have to type in each sql command separately - the Access query builder only allows ONE SQL statement at a time.
So you could type in first above SQL, hit "!" to execute, and then do the two additional SQL statements.
MAKE A BACK-UP!!!
And of course any code, any queries, any reports etc. that used the old column name will break. So changing column names in an existing application is a HIGH RISK adventure (you can and will break tons of code, existing forms, and existing reports, and existing SQL queries you have now).
However, if this is a one-time update? Then I would of course just use the table designer. It allows a re-name without a column drop – and it keeps other field settings such as indexes, format etc.
I which above suggested approach makes the most sense will depend on your particular "use" case.
Last but not least? You can use VBA code and the table objects in that code. This approach is probably the best. It does not use SQL DDL, and you have greater control over a lot of features for a given column (required, allow nulls – the list goes on). Most of these settings CAN be set in DDL - but you spend quite a bit of time searching and looking up those settings.
All in all? I would use the table designer if possible here.
I have a query for a report based on an MS Access database (as the program project file). The tables in this database get updated with new fields periodically as new features are added.
We need to be able to support old and new versions of the file for our report, so need to know if there is a way to insert a field into the SQL SELECT query if it does not already exist. (Note: Do not want to create ALTER TABLE type statements, as the field only needs to be added into the result set, not into the table permanently.)
I know you can do something like "" AS [FieldName], but that only applies when you know the field doesn't exist and need to create a blank spot for it (such as when a unioned table does have that field). In this case, the table might have the field so I want to use it if it does, but if it doesn't I want to have it still exist in the query results with a default value.
Any help would be appreciated. (I also know you can force the user to update the file, but that option was stated as "only last resort".)
Thanks,
Chris
I am using SSMA to convert from an Access db to a SQL 2019 DB.
There are some things I need to fix in the access DB so I am trying to figure out whether or not these things can be done via a query in access or you have to use the goofy UI and do everything manually.
So I had a couple of questions about queries in Microsoft Access:
Can you modify the 'required' attribute on a column within a table by using a query?
Can you configure Index (dupes) on a column by using a query?
Can you change validation rules using a query?
Can you create/delete relationships using a query?
Can you change the field length of a column by using a query?
Any examples of any of these would be helpful, when I google for ms access related things all of the content is either related to Access 2007/2010 or its very UI heavy rather than Query heavy.
I am trying to script this because I may have to do this migration several times.
Update: I was able to get most of what i needed figured out..
ALTER TABLE Users ALTER COLUMN Type CHECK(In ("I","U","") Or Is Null);
Still havent found a way to change the 'ValidationRule'.. trying to change it to
In ("I","U","") Or Is Null
Look into the Data Definition Language section of the MS Access SQL Reference, specifically the ALTER TABLE statement, which will cover the majority of your questions.
For example, in response to:
Can you change the field length of a column by using a query?
ALTER TABLE Table1 ALTER COLUMN Field1 TEXT(100)
The above will change the data type of the field Field1 within table Table1 to a text field accommodating 100 characters.
I am writing a database abstraction layer that also abstracts some of the different query types. One of them is called "field_exists" - its purpose should be pretty self-explanatory.
And I want to implement that for SQLite.
The problem I am having is that I need to use one query that either returns a row confirming that the field exists or none if it doesn't. Thus, I cannot use the PRAGMA approach.
So, what query can I use to check whether a field exists in SQLite, that fulfills the above criteria?
EDIT: I should add that the query needs to be able to run in PHP code (using PDO).
Also, the query should look something like this (which only works with MySQL):
SHOW COLUMNS FROM table LIKE 'field'
Trying to select a field that doesn't exist will return an exception, then you can catch it and return nothing.
Use the .schema TABLENAME command. It will tell you the command that was issued to create the table. For more info chekcout the SQLite command shell documentation.
If you don't have access to the sqlite command line, you can always query the sqlite_master table. Let's say you want to know the command used to create the table MyTable. You'd issue this:
select sql from sqlite_master where name='MyTable';
This then gives you the sql command that was used to create the table. Then just grep through that output and see if the column you're looking for is in the command used to create the table.
UPDATE 2:
Actually better than the sql I posted above, you can use this:
PRAGMA table_info(*table_name*)
This will show you all the columns in a given table along with their types and other info.
My scenario:
I can change the ordinal position of a column in a table.Is there a way to change the ordinal position of a column in a table without recreating the table?
No, you have to recreate the table if you wish to achieve this. (SQL SERVER)
Even when you do this in SSMS, you will see that the script that is generated also recreates the table.
Not in SQL Server - Not sure about other RDBMSs.
You can create a View with the desired ordinal positions but the only time I can think that would be useful is if you are using SELECT * which is a practice that should be avoided anyway.
Hi it depends on the database system you use.
For example in some it is possible to remove and add a column and you can do it in a procedure part where you also can refill it.
But in general it shouldn't matter as you can define the returned data order in your select statement. Is not that enough for you?
Without recreating the Table is Not possible. However, if your concern is about loosing the data here is an option provided by SQl Server Management Studio.
Note: I have used Sql Server 2019 Developer Edition.
Right Click on the Table name and Choose Design Option
Using your Cursor Drag the position of your Column to your desired Position
SQlServer Table Design Options
If you want to do it at script level, You can see the idea below provided by SSMS
Enable the "Auto Generate Change Script" Option available in Tools Menu --> Options --> Designers --> Table and Database Designers.
Enabling the Auto Generate Change Script Option
When you drag the Column in SSMS it will automatically creates the Script for you.
The High level Idea in the auto generated Script is,
Creating a Table with Temp_YourTableName with desired Order of Columns
Copying all the Data from the Original Table to new Temp_YourTableName
Drop the Original Table
Renaming the Temp_YourTableName to Original YourTableName
of course doing everything with Transaction scope to avoid any data loss while the script is executing.
I found a good reason why some time we need to do this here. Interestingly, it is based on Context and not to do anything with Technical.
Say for example, Original Address Table Contains, Street Address 1, City, State, Zip and Country columns. If the requirement Changes to include a new Columns like Street Address 2 this would be meaning full.