data_types.hlp

关系型数据库 Postgresql 6.5.2

.pgaw:Help.f.t configure -tabs {130 300 450}
.pgaw:Help.f.t insert end \
"Data types\n\n" {title} \
"Postgres has a rich set of native data types available to users. Users may add new types to Postgres using the DEFINE TYPE command described elsewhere. 

In the context of data types, the following sections will discuss SQL standards compliance, porting issues, and usage. Some Postgres types correspond directly to SQL92-compatible types. In other cases, data types defined by SQL92 syntax are mapped directly into native Postgres types. Many of the built-in types have obvious external formats. However, several types are either unique to Postgres, such as open and closed paths, or have several possibilities for formats, such as the date and time types. 

" {} \
"Postgres Type\tSQL92 or SQL3 Type\tDescription\n" {bold} \
"bool\tboolean\tlogical boolean (true/false)
box\t\trectangular box in 2D plane\tchar(n)
character(n)\t\tfixed-length character string
cidr\t\tIP version 4 network or host address
circle\t\tcircle in 2D plane
date\tdate\tcalendar date without time of day
float4/8\tfloat(p)\tfloating-point number with precision p
float8\treal, double precision\tdouble-precision floating-point number
inet\t\tIP version 4 network or host address
int2\tsmallint\tsigned two-byte integer
int4\tint, integer\tsigned 4-byte integer
int4\tdecimal(p,s)\texact numeric for p <= 9, s = 0
int4\tnumeric(p,s)\texact numeric for p == 9, s = 0
int8\t\tsigned 8-byte integer
line\t\tinfinite line in 2D plane
lseg\t\tline segment in 2D plane
money\tdecimal(9,2)\tUS-style currency
path\t\topen and closed geometric path in 2D plane
point\t\tgeometric point in 2D plane
polygon\t\tclosed geometric path in 2D plane
serial\t\tunique id for indexing and cross-reference
time\ttime\ttime of day
timespan\tinterval\tgeneral-use time span
timestamp\ttimestamp with time zone\tdate/time
varchar(n)\tcharacter varying(n)\tvariable-length character string

Note:  The cidr and inet types are designed to handle any IP type but only ipv4 is handled in the current implementation. Everything here that talks about ipv4 will apply to ipv6 in a future release.

" {} \
"Postgres Function Constants

Postgres Function\tSQL92 Constant\tDescription" {bold} \
"
getpgusername()\tcurrent_user\tuser name in current session
date('now')\tcurrent_date\tdate of current transaction
time('now')\tcurrent_time\ttime of current transaction
timestamp('now')\tcurrent_timestamp\tdate and time of current transaction
" {}