Firebird database supports read-only columns. Columns that have their values computed, not updated. If I map some table with read-only columns using MyBatis Generator I receive the following error while inserting into or updating the table:
org.firebirdsql.jdbc.FBSQLException: GDS Exception. 335544359. attempted update of read-only column.
How to treat this kind of column using MyBatis Generator? Is it possible to have insert and update statements ignoring this kind of column?
Note:
Using insertSelective and updateSelective passing the read-only columns values as null, instead of using insert and update, will solve only the cases where I don't want to update other fields to null. So, I need another solution.
MyBatis does not offer additional support to read-only columns. So, the turnaround solution is to set the read only columns with the ignoreColumn tag and to write the queries that need that column value manually, using #Select annotations in mappers.
<table tableName="...">
...
<ignoreColumn column="<read only column>" />
...
</table>
Related
Setup:
liquibase 3.3.5
PostgreSQL 9.3
Windows 7 Ultimate
Having set the Liquibase.properties file with
changeLogFile = C://temp/changeset.xml,
I created a diff file with Liquibase (3.3.5).
liquibase.bat diffChangeLog
Examination of the changeset.xml file shows
-<addColumn tableName="view_dx">
<column type="int8" name="counter" defaultValueNumeric="0" defaultValue="0"/>
</addColumn
Problem is when
liquibase.bat update
is run, the changed table is NOT in the same column order as the reference table. This causes issues with the stored procedures using SETOF to return table rows.
Without destroying the existing table on the target database, how can column order be enforced using Liquibase?
TIA
I don't think that you can, in general, get Liquibase to enforce a column ordering. You will probably need to change your stored procedures to use column names rather than relying on position, which is a good habit to get into anyway.
Have you tried using afterColumn attribute of addColumn tag ?
When I add a column in the database, under what conditions do I need to update my EDMX?
To elaborate:
I know if I add a non-nullable field, I need to update the model if I want to write to the database. What if just I want to read?
What if it's a nullable field? Can I both read and write?
What if I were to change the primary key to the new column but the edmx still has the old column as primary?
1) If you want to port an old database, you need to make sure that every table in your database must have a primary key. This is the only requirement for creating the EDMX.
2) If you've added a column in a table at database side, and have not updated edmx, then you'll simply not be able to use that column though EntityFramework.
If you create a non nullable column with no default value, the insert operation will fail with exception "Cannot insert null into column , statement terminated". And the you'll not be able to read values of that column using entityframeowrk, unless you update the edmx.
3) If you've changed the primary key of any table at database side, and if the edmx is not aware of that, your application might create a runtime exception when performing operations with that table.
Remember, Entity Framework creates SQL queries depending upon its knowledge of database(which is defined in EDMX). So if EDMX is incorrect, the resulting SQL queries so generated might lead to problems at runtime.
I wanted to prepare a load utility to load the data into DB2 table. The table has columns which contains GENERATEDALWAYS feature set.
So, I am not able to load an unloaded details from the table.
Is it possible to use import for tables having columns with GENERATEDALWAYS set?
Steps I did:
1. db2 "export to tbl.txt of del modified by coldel| select * from <schema.table> where col=value"
2. db2 "delete from <schema.table> where col=value"
3. db2 "import from tbl.txt of del modified by coldel| allow write access warningcount1 insert into <schema.table>"
The columns with "GENERATEDALWAYS" is having NEW Value after import. Is it possible to use import to populate GENERATEDALWAYS columns to have the old values?
Appreciate the assistance.
Thanks,
Mathew Liju
What you are asking is not possible. With IMPORT you can't override columns that have GENERATED ALWAYS. As #Peter Miehle suggests you could alter the table to specify that the column is GENERATED BY DEFAULT, but this may break other applications.
Your question's title implies that you don't want to use the LOAD utility (but you don't mention anything about it in the actual question). However, LOAD is the only way to write data into the table and maintain the values for the generated column as they exist in the file:
db2 "load from tbl.txt of del modified by generatedoverride insert into schema.table"
If you do this, be aware that:
DB2 does not check if there are conflicts with existing rows in the table. You would need to define a unique index on the column(s) in question to resolve this; this would cause DB2 to delete the rows that you just loaded in the DELETE phase of the load.
If your generated column(s) are using IDENTITY, make sure that you alter the column to ensure that future generated values do not conflict with the rows that you just inserted into the table.
maybe you can drop the "generation" from the column and add it after importing with the appropriate values again.
#Ian Bjorhovde has given you the options.
IMPORT actually does INSERTs in the background - ie, it first prepares a INSERT statement with parameter markers and uses the values in the input file for those markers.
In your SQL snapshot you will see INSERT statement that is used.
Anything that is not possible in an INSERT statement isn't possible with IMPORT (kind of .. )
Can i add multiple columns to a table in a single query execution, using alter table?
No,you can't add multiple columns in single query execution. SQLite supports a limited subset of ALTER TABLE.therefore you have to add them one by one.
see documentation at sqlite
I am sure I am not the first one to struggle with this.
I am using Entity Framework 1 (VS2008) and one of the columns in the table is ModifiedDate. It has DefaultValue in SQL Server (getdate()); so I would like to leave it the DB to do the generation. However, generated SQL has INSERT (... ModifiedDate) VALUES (... null), and the default value doesn't get inserted.
Is it possible to not specify this column at all?
By setting StoreGeneratedPattern in SSDL.