On 8/6/21 1:11 AM, Pavel Stehule wrote:
2. 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
You can specify end of line delimiter in Perl, Python or PHP. It is
highly advisable to learn a scripting language or two when working with
databases. With all databases, not just Postgres.
3. How may I get postgresql to output the create table
statement(s) for one or more tables of one database?
????
4. 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
5. 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
6. -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.
Interval is a SQL standard data type for adding and subtracting dates.
It is supported by a gazillion of other databases:
https://www.ibm.com/docs/en/informix-servers/12.10?topic=types-sql-datetime-interval-data
https://www.mysqltutorial.org/mysql-interval/
https://www.oracletutorial.com/oracle-basics/oracle-interval/
https://cloud.google.com/bigquery/docs/reference/standard-sql/data-types
The only major database that does not support the interval type is SQL
Server. SQL Server has a major problem with SQL standards. It also
doesn't support FETCHÂ FIRST <n> ROWS ONLY OFFSET <n> syntax. Of course,
this group is not about SQL Server so I'll leave it at that.
--
Mladen Gogala
Database Consultant
Tel: (347) 321-1217
https://dbwhisperer.wordpress.com
