Re: Series of 10 questions about the use of postgresql, generally.

Hi

pá 6. 8. 2021 v 6:46 odesílatel A Z <poweruserm(at)live(dot)com(dot)au> napsal:

> I have been going through the free online book LEARNING postgresql book,
> that has been compiled by Stack Overflow contributors. I have gotten to the
> point where I have the following series of unanswered questions:
>
>
> 1. Are there free script for CREATE TYPE (native type) or types out
> there, online, free for commercial use? With function support, too? Can
> someone reply with a link or a suggestion?
>
> ????

>
> 1. If I am using the COPY command for input and output around *.csv
> files, how may I specify internal tuple delimiters of ',', but at the same
> time also specify an end of line delimeter of ';' ?
>
> you cannot to specify end of line delimiter in Postgres

> 1. How may I get postgresql to output the create table statement(s)
> for one or more tables of one database?
>
> ????

>
> 1. I know that I can use COPY to import or export one database table
> between it and a *.csv file. Can I use it to do this with multiple TABLES
> and *.csv files specified in one COPY COMMAND, or not? How may I use COPY,
> or another default native postgresql function, to export or import create
> table commands to and from a *.csv file?
>
> COPY can be used just for one table in one time

if you want to make DDL command (CREATE TABLE), then you should to run
pg_dump -t tablename -a

>
> 1. In the absence of OS command line instructions, is there an
> internal postgresql way, via COPY or another function for example, to
> backup an entire database, with all its create table statements and all
> insert statements, and any other associated object, in one hit? Or is this
> ill advised?
>
> pg_dump

>
> 1. -How exactly do Intervals work, via themselves and in relation to
> the other provided native datatypes? What are Intervals used for?
>
> Interval is Postgres native type, that helps with work with date
operations that are not possible to map to some basic unit. Internally it
is a structure with numeric fields - years, months, days, hours, seconds.
For example - I can work with a value '3 months', but without knowledge of
the beginning, I cannot say how many days this interval has. You can create
interval value by constructor function make_interval, or directly from
literal, or you can divide two timestamp values.

> 1. When setting up communication to remote databases on remote
> machines, I need to use the OPTIONS() function. It seems to require as its
> first function parameter, the schema of the table (the second parameter)
> that it wants to access. Can I supply a null schema, and still be able to
> reference the remote table, or must I also make use of IMPORT FOREIGN
> SCHEMA?
>
> ????

>
> 1. When I am using INHERITS to setup inheritance between two tables,
> will this mean that all data inserted into the Parent table is
> automatically updated into the Child table(s), or not?
>
> No. Data is always inserted to the child table. When you look at the
parent table, Postgres creates an ad-hoc union of this table and all child
tables.

>
> 1. What does the VARYING keyword do to an applicable type in a create
> table statement? CHARACTER VARYING becomes entirely equivalent to VARCHAR.
> Static, limited types become more dynamic and are unlimited.
>
> char type has fixed size - the content is filled by spaces. character
varying or varchar (these names are synonyms) has dynamic size.

>
> 1. How may I access the log for the details of a normal table, or
> similar?
>
>
????

Maybe you find some reply for your questions in FAQ

https://wiki.postgresql.org/wiki/FAQ

Regards

Pavel