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SQL92 defines string functions with specific syntax. Some of these
are implemented using other Postgres functions.
The supported string types for SQL92 are
char, varchar, and text.
Table 5-4. SQL92 String Functions
Function
Returns
Description
Example
char_length(string)
int4
length of string
char_length('jose')
character_length(string)
int4
length of string
char_length('jose')
lower(string)
string
convert string to lower case
lower('TOM')
octet_length(string)
int4
storage length of string
octet_length('jose')
position(string in string)
int4
location of specified substring
position('o' in 'Tom')
substring(string [from int] [for int])
string
extract specified substring
substring('Tom' from 2 for 2)
trim([leading|trailing|both] [string] from string)
string
trim characters from string
trim(both 'x' from 'xTomx')
upper(text)
text
convert text to upper case
upper('tom')
Many additional string functions are available for text, varchar(), and char() types.
Some are used internally to implement the SQL92 string functions listed above.
Table 5-5. String Functions
Function
Returns
Description
Example
char(text)
char
convert text to char type
char('text string')
char(varchar)
char
convert varchar to char type
char(varchar 'varchar string')
initcap(text)
text
first letter of each word to upper case
initcap('thomas')
lpad(text,int,text)
text
left pad string to specified length
lpad('hi',4,'??')
ltrim(text,text)
text
left trim characters from text
ltrim('xxxxtrim','x')
textpos(text,text)
text
locate specified substring
position('high','ig')
rpad(text,int,text)
text
right pad string to specified length
rpad('hi',4,'x')
rtrim(text,text)
text
right trim characters from text
rtrim('trimxxxx','x')
substr(text,int[,int])
text
extract specified substring
substr('hi there',3,5)
text(char)
text
convert char to text type
text('char string')
text(varchar)
text
convert varchar to text type
text(varchar 'varchar string')
translate(text,from,to)
text
convert character in string
translate('12345', '1', 'a')
varchar(char)
varchar
convert char to varchar type
varchar('char string')
varchar(text)
varchar
convert text to varchar type
varchar('text string')
Most functions explicitly defined for text will work for char() and varchar() arguments.
