I have a table TableWithLongerName which has connection foreign key to TableWithLongName. With Go-Pg I want to retrieve data of TableWithLongerName with data from TableWithLongName embedded to it. But unfortunately TableWithLongName has column VeryLongColumnName.
When I run query.Relation("TableWithLongName") it returns error
can't find column table_with_long_name__very_long_c in Model TableWithLongerName
I have create alias for domain in TableWithLongName but it gets overwritten.
Related
I have a MANAGED table in delta format in databrciks and I wanted to change it to EXTERNAL to make sure dropping the table would not affect the data. However the following code did not change the table TYPE and just added a new table property. How can I correctly convert my managed table to an external table ?
%sql
alter table db_delta.table1 SET TBLPROPERTIES('EXTERNAL'='TRUE')
Describe Table:
# Detailed Table Information
Name
db_delta.table1
Location
dbfs:/user/hive/warehouse/db_delta.db/table1
Provider
delta
Type
MANAGED
Table Properties
[EXTERNAL=TRUE,overwriteSchema=true]
I found the following workaround for the above scenario.
1.Copy the Managed table location to external location
dbutils.fs.cp('dbfs:/user/hive/warehouse/amazon_data_agg','abfss://data#amazondata.dfs.core.windows.net/amzon_aggred/',True)
Now drop the managed table.
drop table amazon_data_agg;
Now create the external table by the schema of the already created table, if there is schema mismatch you will get error.
Now you can append and do all operation
df_agg.write.format('delta').mode('append').option('path','abfss://data#amazondata.dfs.core.windows.net/amzon_aggred/').saveAsTable('amazon_data_agg')
I have a table 'client', which has 3 columns - id, siebel_id, phone_number.
PhoneNumber has a unique constraint. If I save a new client with an existing number, I'll get an error ERROR: duplicate key value violates unique constraint "phone_number_unique".
Is it possible to make PSQL or MyBatis showing 'siebel_id' of a record where the phone number already saved?
I mean to get a message like
'ERROR: duplicate key value violates unique constraint "phone_number_unique"
Detail: Key (phone_number)=(+79991234567) already exists on siebel_id...'
No, it's not possible to tweak the internal message that the PostgreSQL database engine returns accompannying an error. Well... unless you recompiled the whole PostgreSQL database from scratch, and I would assume this is off the table.
However, you can easily search for the offending row using SQL, as in:
select siebel_id from client where phone_number = '+79991234567';
I'm using CRecordset to query one table, but I use a second table to filter data. If in my GetDefaultSQL override method I return a table list with more than one table then I get this ERROR: column reference "ctid" is ambiguous. I know what a "ctid" column is, but I don't use it in my code. It's inserted into the original SQL statement by ODBC driver. How to fix this? How to tell the ODBC driver not to insert the "ctid" column?
I tried to call CRecordset::Open with readOnly parameter, as I assume that ODBC needs ctid to update the row, and I don't need to update them. But the error remains.
Also tried to add a primary key to the second table that was missing it, thinking if a table has a primary key then ODBC can use that instead of 'ctid', but again no luck. Makes sense though, because I don't fetch any column of that second table, and the second table is used just for filtering.
If I make a DB view to work around the issue, I get ERROR: column "ctid" does not exist.
You have to call CRecordset::Open with two parameters changed:
m_pSet->Open(CRecordset::snapshot, NULL, CRecordset::readOnly);
Then you can fetch both the joined tables and the view without errors. No "ctid" then.
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 am trying to use Entity Framework DB first to do quick prototyping of a reporting website for a huge db. The problem is one of the tables doesn't have a key. I got an 'Error 159: EntityType has no key defined'. If I add a key on the model designer, I got 'Error 3024: Must specify mapping for all key properties'. My question is whether there is a way to workaround this WITHOUT adding a key to the table. The table is not in our control.
Huge table which does not have a key? It would not be possible for you or for table owner to search for anything in this table without using full table scan. Also, it is basically impossible to use UPDATE by single row without having primary key.
You really have to either create synthetic key, or ask owner to do that. As a workaround, you might be able to find some existing column (or 2-3 columns) which is unique enough that it can be used as unique key. If it is unique but does not have actual index created, that would be still not good for performance - you should create such index.