SQL Functions
SQL Functions
SQL functions are built into Oracle and are available for use in various appropriate SQL statements. Do not confuse SQL functions with user functions written in PL/SQL.
If you call a SQL function with an argument of a datatype other than the datatype expected by the SQL function, then Oracle implicitly converts the argument to the expected datatype before performing the SQL function. If you call a SQL function with a null argument, then the SQL function automatically returns null. The only SQL functions that do not necessarily follow this behavior are CONCAT, NVL, and
REPLACE.
In the syntax diagrams for SQL functions, arguments are indicated by their datatypes. When the parameter "function" appears in SQL syntax, replace it with one of the functions described in this section. Functions are grouped by the datatypes of their arguments and their return values.
Note: When you apply SQL functions to LOB columns, Oracle creates temporary LOBs during SQL and PL/SQL processing. You should ensure that temporary tablespace quota is sufficient for storing these temporary LOBs for your application.
See Also:
■"User-Defined Functions" on page 6-222 for information on user functions
■Oracle Text Reference for information on functions used with Oracle Text
■"Data Conversion" on page 2-48 for implicit conversion of datatypes
The syntax showing the categories of functions follows:
6-2 Oracle9i SQL Reference
SQL Functions
function::=
single_row_function
aggregate_function
analytic_function
object_reference_function
user_defined_function
single_row_function::=
number_function
character_function
datetime_function
conversion_function
miscellaneous_single_row_function
The sections that follow list the built-in SQL functions in each of the groups illustrated in the preceding diagrams except user-defined functions. All of the built-in SQL functions are then described in alphabetical order. User-defined functions are described at the end of this chapter.
Single-Row Functions
Single-row functions return a single result row for every row of a queried table or view. These functions can appear in select lists, WHERE clauses, START WITH and CONNECT BY clauses, and HAVING clauses.
Number Functions
Number functions accept numeric input and return numeric values. Most of these functions return values that are accurate to 38 decimal digits. The transcendental functions COS, COSH, EXP, LN, LOG, SIN, SINH, SQRT, TAN, and TANH are accurate to 36 decimal digits. The transcendental functions ACOS, ASIN, ATAN, and ATAN2 are accurate to 30 decimal digits. The number functions are:
ABS
ACOS
ASIN
Functions 6-3
SQL Functions
ATAN
ATAN2
BITAND
CEIL
COS
COSH
EXP
FLOOR
LN
LOG
MOD
POWER
ROUND (number)
SIGN
SIN
SINH
SQRT
TAN
TANH
TRUNC (number)
WIDTH_BUCKET
Character Functions Returning Character Values
Character functions that return character values return values of the same datatype as the input argument.
■Functions that return CHAR values are limited in length to 2000 bytes.
■Functions that return VARCHAR2 values are limited in length to 4000 bytes.
For both of these types of functions, if the length of the return value exceeds the limit, then Oracle truncates it and returns the result without an error message.
■Functions that return CLOB values are limited to 4 GB.
For CLOB functions, if the length of the return values exceeds the limit, then Oracle raises an error and returns no data.
The character functions that return character values are:
CHR
CONCAT
INITCAP
LOWER
6-4 Oracle9i SQL Reference
SQL Functions
LPAD
LTRIM
NLS_INITCAP
NLS_LOWER
NLSSORT
NLS_UPPER
REPLACE
RPAD
RTRIM
SOUNDEX
SUBSTR
TRANSLATE
TREAT
TRIM
UPPER
Character Functions Returning Number Values
Character functions that return number values can take as their argument any character datatype.
The character functions that return number values are:
ASCII
INSTR
LENGTH
Datetime Functions
Datetime functions operate on values of the DATE datatype. All datetime functions return a datetime or interval value of DATE datatype, except the MONTHS_BETWEEN function, which returns a number. The datetime functions are:
ADD_MONTHS
CURRENT_DATE
CURRENT_TIMESTAMP
DBTIMEZONE
EXTRACT (datetime)
FROM_TZ
LAST_DAY
LOCALTIMESTAMP
MONTHS_BETWEEN
NEW_TIME
Functions 6-5
SQL Functions
NEXT_DAY
NUMTODSINTERVAL
NUMTOYMINTERVAL
ROUND (date)
SESSIONTIMEZONE
SYS_EXTRACT_UTC
SYSDATE
SYSTIMESTAMP
TO_DSINTERVAL
TO_TIMESTAMP
TO_TIMESTAMP_TZ
TO_YMINTERVAL
TRUNC (date)
TZ_OFFSET
Conversion Functions
Conversion functions convert a value from one datatype to another. Generally, the form of the function names follows the convention datatype TO datatype. The first datatype is the input datatype. The second datatype is the output datatype. The SQL conversion functions are:
ASCIISTR
BIN_TO_NUM
CAST
CHARTOROWID
COMPOSE
CONVERT
DECOMPOSE
HEXTORAW
NUMTODSINTERVAL
NUMTOYMINTERVAL
RAWTOHEX
RAWTONHEX
ROWIDTOCHAR
ROWIDTONCHAR
TO_CHAR (character)
TO_CHAR (datetime)
TO_CHAR (number)
TO_CLOB
TO_DATE
TO_DSINTERVAL
6-6 Oracle9i SQL Reference
SQL Functions
TO_LOB
TO_MULTI_BYTE
TO_NCHAR (character)
TO_NCHAR (datetime)
TO_NCHAR (number)
TO_NCLOB
TO_NUMBER
TO_SINGLE_BYTE
TO_YMINTERVAL
TRANSLATE ... USING
UNISTR
Miscellaneous Single-Row Functions
The following single-row functions do not fall into any of the other single-row function categories:
BFILENAME
COALESCE
DECODE
DEPTH
DUMP
EMPTY_BLOB, EMPTY_CLOB
EXISTSNODE
EXTRACT (XML)
EXTRACTVALUE
GREATEST
LEAST
NLS_CHARSET_DECL_LEN
NLS_CHARSET_ID
NLS_CHARSET_NAME
NULLIF
NVL
NVL2
PATH
SYS_CONNECT_BY_PATH
SYS_CONTEXT
SYS_DBURIGEN
SYS_EXTRACT_UTC
SYS_GUID
SYS_TYPEID
SYS_XMLAGG
Functions 6-7