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May
27
comment Troubleshooting high disk read - buffer cache query
Which DBMS are you using? Postgres? Oracle?
May
27
comment GROUP BY very slow when returning many rows
wiki.postgresql.org/wiki/Slow_Query_Questions
May
27
comment A question about oracle upgrade from 12.0.0.1 to 12.0.0.2 using dbua
There is neither a version named 12.0.0.1 nor 12.0.0.2
May
26
comment Why have both a postmaster and postgres executable?
There is another thing to consider: (at least) on Windows pg_ctl will drop elevated privileges and thus allows to start Postgres through an administrative account. Running postgres.exe directly will fail. I don't know if that is the same on Linux (postgres refusing to run as root) or if this behavior (dropping elevated privileges) could have been built directly into the postgres binary as well.
May
24
comment How is encoding done in SQL database tables for pattern matching?
much faster is debatable and depends a lot on the DBMS being used: depesz.com/2012/06/07/123-vs-depesz-what-is-faster
May
22
comment Dividing values from a single column into 2 based on a rule
Which DBMS are you using? Postgres? Oracle?
May
21
comment Left Outer Join doesn't give expected result. What am I missing?
b.fld will be null if the outer join does not find a corresponding row.
May
21
comment Postgres Query Optimisation (Rails App)
For a statement processing all rows of a table, there is not much you can do - indexes will never help for that. If you are on 9.4 already you might try to use the new filter() expression instead of the case - sometimes that improves the performance (but then not much I would assume)
May
20
comment how to migrate data between two distincts tables
If the new table is in a different database: export the data using a COPY and an appropriate SELECT statement. Then import the data in the target database e.g. using COPY again. If the new table is in fact in the same (physical) database, you can do an insert into new_table ... select ... from old_table (provided you can do the "transformation" in pure SQL)
May
18
comment Does MariaDB support schema changes inside a transaction?
from the manual: "DDL statements (CREATE, ALTER, DROP) [...] cause an implicit COMMIT"
May
18
comment How to set correctly utf8 on oracle?
That's your SQL client (presumably SQL*Plus) which cannot display those characters. You need to use a font that can display them and in case of SQL*Plus you also need to switch the command line from which you start SQL*Plus to UTF-8 (I think that is done through chcp 65001)
May
17
comment What are the compression options for storing large amounts of text in Postgres?
from the manual: "Long strings are compressed by the system automatically" and here is a more detailed description: postgresql.org/docs/current/static/storage-toast.html
May
16
comment Oracle database for learning purposes
There is no Oracle Express edition for OS-X (actually I think there is no Oracle version for OS-X at all). However you can download a VirtualBox image that contains a pre installed environment: oracle.com/technetwork/community/developer-vm/index.html#dbapp (that is however Oracle 12 - if you really need Oracle 11, then you need to download the version for Linux and install that manually in a VirtualBox environment: oracle.com/technetwork/database/database-technologies/…
May
16
comment Oracle Equivalent of the following SQL Server syntax
What does it do?
May
15
comment Managing View Dependencies
Use a schema management tool like Liquibase or Flyway
May
15
comment How to work with multiple Postgres databases in psycopg2
I don't know Python, but in Postgres it's in general not possible to do cross database queries. If you need that on a regular basis (e.g. joining tables) you are better off putting everything in one database, but separate things using schemas. A possible workaround is to use a foreign data wrapper in one DB to expose the tables in the other DB - but that will be much slower than putting everything into a single DB.
May
15
comment How to GRANT/REVOKE user permissions for user on Firebird 1.5?
Regarding the documentation fragmentation: if I want to find out if a feature is present in V2.5, do I need to search the language reference update for Firebird 1.0 and 1.5 and 2.0 and 2.5 or is it sufficient to only look into the update for 2.5? Are the "update manuals" cumulative?
May
15
comment Unable to grant permission on table
Then I'll repeat my question: "Did you create that account yourself? If yes how and with which privileges?" - just because a user is called root, doesn't mean he has any special privileges
May
15
comment Unable to grant permission on table
@Greenonline: no, you don't need root access to the database server. You don't even need shell access to the database server - you only need to be able to connect to the Postgres server using a SQL tool (e.g. psql)
May
15
comment Unable to grant permission on table
What do you mean with root user? By default there is no user named "root" in Postgres. Did you create that account yourself? If yes how and with which privileges?