Hi pá 6. 8. 2021 v 6:46 odesílatel A Z <powerus...@live.com.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
