With reference to http://hsqldb.org/doc/2.0/guide/compatibility-chapt.html#coc_compatibility_mysql, the compatibility only solves half the problem. THE CAPITALIZED RESULTSETMETADATA (COLUMN NAMES) IS A PROBLEM! This complicates testing with the in-memory database when the MySQL is used in production. I have to sprinkle code in my controllers / verticles to check which database is used (test or non-test) and format the SQL query string by double-quoting the column names in the query.
Related post: Java common JDBC SQL Query strategy for Unit Test using HSQLDB and runtime using MySQL
Question: How to use lower-case column names or how to convert the capitalized RESULTSETMETADATA returned from HSQLDB to lower case?
Solution: Ditch HSQLDB and use H2 with database_to_upper=false option.
Related
I'm using DBeaver to write script for my PostgreSQL database.
I have a PostgreSQL DB with Tables autogenerated by C#/EFCore (Microsoft ORM) - I receive SQL Error [42P01] if I don't add double quotes around table names when I cut and paste my ORM queries to DBeaver. I got [42703] for fields without double quotes. I do not have to add double quotes in C# code but it appears to be required in DBeaver?
example:
select * from Dnp3PropertyBase => SQL Error [42P01]
select * from "Dnp3PropertyBase" => OK, all results shown...
Does anybody know if I can change a parameter in DBeaver somewhere in order to enter table names and fields without double quotes?
Note: Using DBeaver 22.3.2 (latest on 2023-01-11)
Update After reading: Postgresql tables exists, but getting "relation does not exist" when querying
show search_path => public, public, "$user"
SELECT * FROM information_schema.tables => All tables are in public schema
SELECT * FROM information_schema.columns => All columns are in public schema
Question: How to be able to cut and paste my EFCore generated queries from Visual Studio output window to DBeaver query without having any errors regarding table names and field names?
First let me copy #a_horse_with_no_name comment:
Unquoted names are folded to lower case in Postgres (and to uppercase
in Oracle, DB2, Firebird, and many others). So SomeTable is in fact
stored as sometable (or SOMETABLE). However quoted identifiers have to
preserve the case and are case sensitive then. So "SomeTable" is
stored as SomeTable
Many peoples recommended me to go with snake case which I didn't want to go with initialy because all tables were auto generated by EF Core (Microsoft C# ORM). I told myself that Microsoft would do standard things. Microsoft use the exact "class" name in code as the table name , by default. That appears to me very logical in order to stay coherent and apply the same rules everywhere. C# recommended to use Camel case for classes so each table names end by default in Camel case instead of snake case.
PostgreSQL seems to promote users to use snake casing because they lower case every non double quoted names. According to a_horse_with_no_name, and I think the same, only PostgreSQL has the behavior of lower casing down every table names and field names which are not double quoted in SQL script. That behavior (changing casing for non double quoted names) appears to me as being very limitative. It also has hidden effect that could be hard to find for non initiated peoples coming from other DB world.
According to PostgreSQL doc, they recommend to use nuget package (.UseSnakeCaseNamingConvention()). It probably works fine for TPH (table per hierarchy) which is recommended by Microsoft for performance. But it does not works for table name for TPC (table per class) because of actual bugs in EFCore 7 (see Github project).
I received that message at the end of "update-database":
Both 'WindTurbine' and 'ResourceGenerator' are mapped to the table
'resource_generator'. All the entity types in a non-TPH hierarchy (one
that doesn't have a discriminator) must be mapped to different tables.
See https://go.microsoft.com/fwlink/?linkid=2130430 for more
information.
PostgreSQL doc : TPH supported OK but not for table in TPC (2023-01-12). I use TPC then I had to force each table name directly through TableAttribute.
My solution For table name, I use snake casing by manually add a "Table" attribute to each of my classes with the proper name like this sample:
[Table("water_turbine")]
public class WaterTurbine : ResourceGenerator
For fields, I use the EFCore.NamingConventions NugetPackage which works fine for fields names. Don't forget that if you have 2 classes mapped to the same object, it is because you are using TPC and did not force table name through TableAttribute.
This way all my table and fields names are snake casing and I can cut and paste any query dumped in my debugger directly in any SQL script window of DBeaver (or any SQL tool).
I have a sequence in my database, which I generated through Liquibase. During refactoring, we decided that we didn't like the name that we gave it, and we would like to rename it, preserving all data that currently exists for it.
It seems possible to alter a sequence, but I'm not seeing anything about how to rename the sequence. Is there a way to do it, or a reasonable workaround?
(If it matters, I'm using Oracle SQL)
Although not documented, this refactoring is supported by Liquibase. Not sure what version this change was implemented in, but the class supporting the feature was commited on 30 Jan 2014. What's interesting though, is that the original issue is still unresolved.
Anyway, the refactoring is supposed to be working only on Oracle and Postgres. I've tested it on Oracle with Liquibase 3.4.1:
databaseChangeLog:
- changeSet:
id: change_set_id
author: me
dbms: oracle
changes:
- renameSequence:
oldSequenceName: old_name_seq
newSequenceName: new_name_seq
The above refactoring is in YAML format, but you could easily guess its XML counterpart.
On Oracle, this generates the following statement:
RENAME old_name_seq TO new_name_seq;
2 other supported parameters are catalogName and schemaName.
There is not currently a built-in refactoring to rename a sequence. If your database engine supports it, you could execute whatever methods are supported using a <sql> or <sqlFile> change.
You said you were using Oracle SQL. The RENAME statement allows for renaming a sequence. So your Liquibase script would look like this:
<sql>RENAME old_sequence_name TO new_sequence_name</sql>
I've got a strange problem. A customer named a field in FirebirdSQL start. Now I cannot select this field:
select t.start from table t
Gives me the error: Invalid token
Any idea on how I can select this field?
The word start is a reserved word in Firebird and therefor needs to be quoted. The quote symbol in Firebird is the double quote. So you need to use:
select t."start" from "table" t
Note that I quoted table as well, as it is also a reserved word. Quoting makes the name case sensitive, so you may need to use "START" and "TABLE".
In your comments you mention that quoting yields a constant value 'table'. This means that you are using dialect 1, the deprecated (and legacy) dialect of Firebird. This legacy dialect cannot quote object names, and the double quote is for string literals (next to the SQL standard single quotes). Either your database is a dialect 1 database, or you specified the wrong connection dialect in your connection library.
If you database is actually dialect 3, solving this is as simple as specifying connection dialect 3 (or 0 to auto select based on the database dialect). However if your database is a dialect 1 database you will need to migrate to dialect 3 to be able to solve this.
If this is simply to try things out: make sure you create a dialect 3 database (for most tools this is the default).
How to determine database dialect
To determine the database dialect, you can use the gstat tool:
gstat mydatabase.fdb -header
In recent Firebird versions you can also query the MON$DATABASE monitoring table. Most query tools also allow you to view the database properties.
How to migrate from dialect 1 to dialect 3
That is I think too complicated to write down here (and I have never done it myself as it was considered deprecated years ago). However the Interbase 6.0 Getting Started (available from Firebird: Reference Manuals (at the end of the page) describes the basic process of migration, and I am sure that there are pages to be found with some googling.
I had understood that jOOQ would simulate SQL MERGE on systems (such as PostgreSQL) that don't support it.
I have a table with a serial (autoincrement) "id" column and a string "uri" column. I want to use numeric IDs instead of URIs in my database, so I have to make sure I have a URI in the ID lookup table. So following the example in the jOOQ manual, I thought this would work:
createDSLContext().mergeInto(tableByName("uris"))
.using(createDSLContext().selectOne())
.on(fieldByName("uri").equal("http://example.com/"))
.whenNotMatchedThenInsert(fieldByName("uri"))
.values("http://example.com/").execute();
This gives me a DataAccessException saying something like:
SQL [merge into "uris" using (select 1) on "uri" = ? when not matched then insert ("uri") values (?)]; ERROR: syntax error at or near "merge"
But then the log says jOOQ goes ahead and tries to execute the query with bind values. But the table is never updated. So I'm guessing the jOOQ doesn't simulate MERGE on PostgreSQL?
So I then try the H2 database syntax:
createDSLContext().mergeInto(tableByName("uris"), fieldByName("uri")).values(uri.toString()).execute();
I get:
The H2-specific MERGE syntax is not supported in dialect : POSTGRES
What!? But the jOOQ documentation says that the H2 syntax "can be fully simulated by jOOQ for all other databases that support the SQL standard." Surely PostgreSQL supports the SQL standard. Does it really mean "...the SQL standard version of MERGE?"
Is there any way to get PostgreSQL support for MERGE via jOOQ, or am I stuck doing the same workarounds I would do anyway?
To be sure if a given SQL feature is supported by jOOQ for your database, please consider the Javadoc's #Support annotation on the relevant DSL method. This is also documented in the manual. In this case, DSLContext.mergeInto(), where you can see that this statement is currently only supported for these SQLDialects:
#Support(value={CUBRID,DB2,HSQLDB,ORACLE,SQLSERVER,SYBASE})
MERGE is a very powerful statement that is not really easy to emulate if your database doesn't natively support it.
"can be fully simulated by jOOQ for all other databases that support the SQL standard." Surely PostgreSQL supports the SQL standard. Does it really mean "...the SQL standard version of MERGE?"
Yes of course, the SQL standard MERGE statement must be supported :-) We'll clarify this in the manual. I have registered issue #3183 for this.
Is there any way to get PostgreSQL support for MERGE via jOOQ, or am I stuck doing the same workarounds I would do anyway?
Right now, unfortunately, we don't have a solution for this in PostgreSQL. Feel free to discuss possible solutions on the jOOQ User Group.
Yes , it can support which database support the merge in SQL stand.
but postgresql unsupport this feature in SQL standard.
Please see
F312 MERGE statement
F313 Enhanced MERGE statement
F314 MERGE statement with DELETE branch
http://www.postgresql.org/docs/9.3/static/unsupported-features-sql-standard.html
Is there a way to tell NHibernate to use square brackets for all table and column names (like [MyColumn]) when generating the SQL schema export for MS SQL Server? I have a legacy database that uses reserved names for certain columns and running the SQL script generated using NH throws an error because of it.
I want to avoid having to specify this separately for each column.
UPDATE: I'm using the correct dialect:
MsSqlConfiguration.MsSql2008.ConnectionString(connectionString)
UPDATE 2: #UpTheCreek pointed me in the right direction - backticks, which helped me find the answer in the "NHibernate in Action" book (p. 76):
There is no way, apart from quoting all table and column names in backticks, to force NHibernate to use quoted identifiers everywhere.
Easier approach:
SchemaMetadataUpdater.QuoteTableAndColumns(config)
(Before building SessionFactory)
That will quote all the reserved names automatically.
Use backticks in your mapping files around the column names. NH should replace these with the correct character for your db dialect (in your case square brackets).
i.e. use:
<class name="SomeClass" table="`SomeTable`">
NB - It won't work with an apostrophe. The backtick is located top left on most keyboards.
You need to use (or write) the correct dialect for your database