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SQL92 defines two primary character types:
char and varchar.
Postgres supports these types, in
addition to the more general text type,
which unlike varchar
does not require an explicit declared upper
limit on the size of the field.
Table 3-5. Postgres Character Types
Character Type
Storage
Recommendation
Description
char
1 byte
SQL92-compatible
Single character
char(n)
(4+n) bytes
SQL92-compatible
Fixed-length blank padded
text
(4+x) bytes
Best choice
Variable-length
varchar(n)
(4+n) bytes
SQL92-compatible
Variable-length with limit
There is one other fixed-length character type in Postgres.
The name type
only has one purpose and that is for storage of internal catalog
names.
It is not intended for use by the general user.
Its length is currently defined as 32 bytes (31 characters plus terminator)
but should be reference using NAMEDATALEN.
The length is set at compile time (and is therefore adjustable for
special uses); the default maximum length may change in a future release.
