You can create a new table by specifying the table
name, along with all column names and their types:
CREATE TABLE weather (
city varchar(80),
temp_lo int, -- low temperature
temp_hi int, -- high temperature
prcp real, -- precipitation
date date
);
You can enter this into psql with the line
breaks. psql will recognize that the command
is not terminated until the semicolon.
White space (i.e., spaces, tabs, and newlines) may be used freely
in SQL commands. That means you can type the command aligned
differently than above, or even all on one line. Two dashes
("--") introduce comments.
Whatever follows them is ignored up to the end of the line. SQL
is case insensitive about key words and identifiers, except
when identifiers are double-quoted to preserve the case (not done
above).
varchar(80) specifies a data type that can store
arbitrary character strings up to 80 characters in length.
int is the normal integer type. real is
a type for storing single precision floating-point numbers.
date should be self-explanatory. (Yes, the column of
type date is also named date.
This may be convenient or confusing -- you choose.)
PostgreSQL supports the usual
SQL types int,
smallint, real, double
precision, char(N),
varchar(N), date,
time, timestamp, and
interval, as well as other types of general utility
and a rich set of geometric types.
PostgreSQL can be customized with an
arbitrary number of user-defined data types. Consequently, type
names are not syntactical keywords, except where required to
support special cases in the SQL standard.
The second example will store cities and their associated
geographical location:
CREATE TABLE cities (
name varchar(80),
location point
);
The point type is an example of a
PostgreSQL-specific data type.
Finally, it should be mentioned that if you don't need a table any
longer or want to recreate it differently you can remove it using
the following command:
DROP TABLE tablename;
