Example query is like SELECT * FROM ..EMPLOYEES. What does it mean this query style on SQL Server?
Yes, it SQL Server query syntax.
Full syntax would be :
select *
from Databasename.schema.tablename -- (first two .. optional) will run on selected database with default schema
Where first . denotes for database name, second . for schema
If you are running with this :
select *
from ..EMPLOYEES
So, it will run for default schema dbo with selected database on top.
Transact-SQL references to the name of a database object can be a four-part name in server.[database].[schema].object form and as is mentioned in the documentation ... to omit intermediate nodes, use periods to indicate these positions. The following table shows the valid formats of object names..
So
SELECT * FROM ..EMPLOYEES
is a valid T-SQL statement. The database and schema names are omitted and the default database and schema for the login are used.
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).
have a series of databases on the same server which i am wishing to query. I am using the same code to query the database and would like the results to appear in a single list.
I am using 'USE' to specify which database to query, followed by creating some temporary tables to group my data, before using a final SELECT statement to bring together all the data from the database.
I am then using UNION, followed by a second USE command for the next database and so on.
SQL Server is showing a syntax error on the word 'UNION' but does not give any assistance as to the source of the problem.
Is it possible that I am missing a character. At present I am not using ( or ) anywhere.
The USE statement just redirects your session to connect to a different database on the same instance, you don't actually need to switch from database to database in this matter (there are a few rare exceptions tho).
Use the 3 part notation to join your result sets. You can do this while being connected to any database.
SELECT
SomeColumn = T.SomeColumn
FROM
FirstDatabase.Schema.TableName AS T
UNION ALL
SELECT
SomeColumn = T.SomeColumn
FROM
SecondDatabase.Schema.YetAnotherTable AS T
The engine will automatically check for your login's users on each database and validate your permissions on the underlying tables or views.
UNION adds result sets together, you can't issue another operation (like USE) other than SELECT between UNION.
You should use the database names before the table name:
SELECT valueFromBase1
FROM `database1`.`table1`
WHERE ...
UNION
SELECT valueFromBase2
FROM `database2`.`table2`
WHERE ...
For a query which looks something like
select * from cus_query.ca_activity_vw#drifter
I imagine cus_query is the schema and the view's name is ca_activity_vw. But what is drifter ?
I quote the Oracle documentation:
If the identifier names an object on a remote database, you must reference it with its remote name. The syntax is:
simple_identifier_name#link_to_remote_database
If the identifier is declared in a PL/SQL unit on a remote database, you must reference it with its qualified remote name. The syntax is:
unit_name.simple_identifier_name#link_to_remote_database
From this page : http://docs.oracle.com/cd/E11882_01/appdev.112/e25519/fundamentals.htm#LNPLS99945
drifter is a so-called database link - it allows to transparently query tables that reside on a different database (usually Oracle, but possibly some other RDBMS, e.g. via Database gateway).
To see the definition for the database link, you can use this query (this requires DBA privileges):
select * from dba_db_links
I am creating tables in the GUI of postgreSQL, PgAdmin3. There is an element that seems to be specious in the naming of the tables. The following is my fragmented comprehension of postgreSQL (I could be wrong if I am, please rectify). I am inserting tables in the database using the ETL tool Talend.
When there is only one schema in the database: No reference to the schema is mandatory
select * from tablename
When there is more than one schema in the database: Reference to the schema is mandatory and the reference to the schema is required in quotes
select * from "schema".tablename
There is something new I drifted upon yesterday and I do not know what might be causing pgAdmin to do this:
select * from "schema"."tablename"
I am not oblivious of the part that referencing to the specific schema is mandatory when there is more than one schema present in the same database and in quotes but why does one need to have the table name in quotes as well.
I'm attempting to write an extension for SQL Developer to better support Postgres. These are just XML configuration files with SQL snippets in them. To display the values for a postgres sequence, I need to run a simple query of the following form:
select * from schema.sequence
The trouble with this is that the Oracle SQL Developer environment provides the correct schema and node (sequence) name as bind variables. This would mean that I should format the query as:
select * from :SCHEMA.:NAME
The trouble with this is that bind variables are only valid in the select clause or the where clause (as far as I'm aware), and using this form of the query returns a "syntax error at or near "$1" error message.
Is there a way to return the values in the sequence object without directly selecting them from the sequence? Perhaps some obtuse joined statement from pg_catalog tables?
Try this:
select *
from information_schema.sequences
where sequence_name = :name
and sequence_schema = :schema;
It's not exactly the same thing as doing a select from the sequence, but the basic information is there.