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Help Center/ GaussDB(DWS)/ SQL Syntax Reference/ SQL Syntax Reference (8.1.3.x)/ Functions and Operators/ Type Conversion Functions

Type Conversion Functions

Updated on 2024-12-19 GMT+08:00

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cast(x as y)

Description: Converts x into the type specified by y.

Examples:

    
       SELECT cast('22-oct-1997' as timestamp);
      timestamp      
---------------------
 1997-10-22 00:00:00
(1 row)

hextoraw(string)

Description: Converts characters containing hexadecimal digits in the CHAR, VARCHAR2, NCHAR, or NVARCHAR2 data type to RAW data type.

Return type: raw

Examples:

    
       SELECT hextoraw('7D');
 hextoraw 
----------
 7D
(1 row)

numtoday(numeric)

Description: Converts values of the number type into the timestamp of the specified type.

Return type: timestamp

Examples:

    
       SELECT numtoday(2);
 numtoday
----------
 2 days
(1 row)

pg_systimestamp()

Description: Obtains the system timestamp.

Return type: timestamp with time zone

Examples:

    
       SELECT pg_systimestamp();
        pg_systimestamp
-------------------------------
 2015-10-14 11:21:28.317367+08
(1 row)

rawtohex(string)

Description: Converts the RAW data type value into a hexadecimal string. Each byte in string is converted to a double-byte string.

The result is the ACSII code of the input characters in hexadecimal format.

Return type: varchar

Examples:

    
       SELECT rawtohex('1234567');
    rawtohex    
----------------
 31323334353637
(1 row)

to_char (datetime/interval [, fmt])

Description: Converts a DATETIME or INTERVAL value of the DATE/TIMESTAMP/TIMESTAMP WITH TIME ZONE/TIMESTAMP WITH LOCAL TIME ZONE type into the VARCHAR type according to the format specified by fmt.

The optional parameter fmt includes the following types: date, time, week, quarter, and century. Each type has a unique template. The templates can be combined together. Common templates include: HH, MI, SS, YYYY, MM, and DD.
A template may have a modification word. FM is a common modification word and is used to suppress the preceding zero or the following blank spaces.

Return type: varchar

Examples:

    
       SELECT to_char(current_timestamp,'HH12:MI:SS');
 to_char  
----------
 10:19:26
(1 row)

    
       SELECT to_char(current_timestamp,'FMHH12:FMMI:FMSS');
 to_char  
----------
 10:19:46
(1 row)

to_char(double precision, text)

Description: Converts the values of the double-precision type into the strings in the specified format.

Return type: text

Examples:

    
       SELECT to_char(125.8::real, '999D99');
 to_char 
---------
  125.80
(1 row)

to_char (integer/number[, fmt])

Descriptions: Converts an integer or a value in floating point format into a string in specified format.

The optional parameter fmt can be the following types: decimal characters, grouping characters, positive/negative sign and currency sign. Each type has a unique template. The templates can be combined together. Common templates include: 9, 0, millesimal sign (,), and decimal point (.).
A template can have a modification word, similar to FM. However, FM does not suppress 0 which is output according to the template.
Use the template X or x to convert an integer value into a string in hexadecimal format.

Return type: varchar

Examples:

    
       SELECT to_char(1485,'9,999');
 to_char 
---------
  1,485
(1 row)

    
       SELECT to_char( 1148.5,'9,999.999');
  to_char   
------------
  1,148.500
(1 row)

    
       SELECT to_char(148.5,'990999.909');
   to_char   
-------------
    0148.500
(1 row)

    
       SELECT to_char(123,'XXX');
 to_char 
---------
   7B
(1 row)

to_char(interval, text)

Description: Converts the values of the time interval type into the strings in the specified format.

Return type: text

Examples:

    
       SELECT to_char(interval '15h 2m 12s', 'HH24:MI:SS');
 to_char
----------
 15:02:12
(1 row)

to_char(int, text)

Description: Converts the values of the integer type into the strings in the specified format.

Return type: text

Examples:

    
       SELECT to_char(125, '999');
 to_char
---------
  125
(1 row)

to_char(numeric, text)

Description: Converts the values of the numeric type into the strings in the specified format.

Return type: text

Examples:

    
       SELECT to_char(-125.8, '999D99S');
 to_char
---------
 125.80-
(1 row)

to_char (string)

Description: Converts the CHAR/VARCHAR/VARCHAR2/CLOB type into the VARCHAR type.

If this function is used to convert data of the CLOB type, and the value to be converted exceeds the value range of the target type, an error is returned.

Return type: varchar

Examples:

    
       SELECT to_char('01110');
 to_char
---------
 01110
(1 row)

to_char(timestamp, text)

Description: Converts the values of the timestamp type into the strings in the specified format.

Return type: text

Examples:

    
       SELECT to_char(current_timestamp, 'HH12:MI:SS');
 to_char
----------
 10:55:59
(1 row)

to_clob(char/nchar/varchar/nvarchar/varchar2/nvarchar2/text/raw)

Description: Convert the RAW type or text character set type CHAR/NCHAR/VARCHAR/VARCHAR2/NVARCHAR2/TEXT into the CLOB type.

Return type: clob

Examples:

    
       SELECT to_clob('ABCDEF'::RAW(10));
 to_clob 
---------
 ABCDEF
(1 row)

    
       SELECT to_clob('hello111'::CHAR(15));
 to_clob  
----------
 hello111
(1 row)

    
       SELECT to_clob('gauss123'::NCHAR(10));
 to_clob  
----------
 gauss123
(1 row)

    
       SELECT to_clob('gauss234'::VARCHAR(10));
 to_clob  
----------
 gauss234
(1 row)

    
       SELECT to_clob('gauss345'::VARCHAR2(10));
 to_clob  
----------
 gauss345
(1 row)

    
       SELECT to_clob('gauss456'::NVARCHAR2(10));
 to_clob  
----------
 gauss456
(1 row)

    
       SELECT to_clob('World222!'::TEXT);
  to_clob  
-----------
 World222!
(1 row)

to_date(text)

Description: Converts values of the text type into the timestamp in the specified format.

Return type: timestamp

Examples:

    
       SELECT to_date('2015-08-14');
       to_date
---------------------
 2015-08-14 00:00:00
(1 row)

to_date(text, text)

Description: Converts the values of the string type into the dates in the specified format.

Return type: timestamp

Examples:

    
       SELECT to_date('05 Dec 2000', 'DD Mon YYYY');
       to_date
---------------------
 2000-12-05 00:00:00
(1 row)

to_date(string, fmt)

Description: Converts a string into a value of the DATE type according to the format specified by fmt. This function cannot support the CLOB type directly. However, a parameter of the CLOB type can be converted using implicit conversion.

Return type: date

Examples:

    
       SELECT TO_DATE('05 Dec 2010','DD Mon YYYY');
       to_date       
---------------------
 2010-12-05 00:00:00
(1 row)

to_number ( expr [, fmt])

Description: Converts expr into a value of the NUMBER type according to the specified format.

For details about the type conversion formats, see Table 1.

If a hexadecimal string is converted into a decimal number, the hexadecimal string can include a maximum of 16 bytes if it is to be converted into a sign-free number.

During the conversion from a hexadecimal string to a decimal digit, the format string cannot have a character other than x or X. Otherwise, an error is reported.

Return type: number

Examples:

    
       SELECT to_number('12,454.8-', '99G999D9S');
 to_number 
-----------
  -12454.8
(1 row)

to_number(text, text)

Description: Converts the values of the string type into the numbers in the specified format.

Return type: numeric

Examples:

    
       SELECT to_number('12,454.8-', '99G999D9S');
 to_number
-----------
  -12454.8
(1 row)

to_timestamp(double precision)

Description: Converts a UNIX century into a timestamp.

Return type: timestamp with time zone

Examples:

    
       SELECT to_timestamp(1284352323);
      to_timestamp      
------------------------
 2010-09-13 12:32:03+08
(1 row)

to_timestamp(string [,fmt])

Description: Converts a string into a value of the timestamp type according to the format specified by fmt. When fmt is not specified, perform the conversion according to the format specified by nls_timestamp_format.

In to_timestamp in GaussDB(DWS):

If the input year YYYY is 0, an error will be reported.
If the input year YYYY<0 to specify SYYYY in fmt, the year with the value of n (an absolute value) BC is output correctly.

Characters in the fmt must match the schema for formatting the data and time. Otherwise, an error is reported.

Return type: timestamp without time zone

Examples:

    
       SHOW nls_timestamp_format;
    nls_timestamp_format    
----------------------------
 DD-Mon-YYYY HH:MI:SS.FF AM
(1 row)

SELECT to_timestamp('12-sep-2014');
    to_timestamp     
---------------------
 2014-09-12 00:00:00
(1 row)

    
       SELECT to_timestamp('12-Sep-10 14:10:10.123000','DD-Mon-YY HH24:MI:SS.FF');
      to_timestamp       
-------------------------
 2010-09-12 14:10:10.123
(1 row)

    
       SELECT to_timestamp('-1','SYYYY');
      to_timestamp      
------------------------
 0001-01-01 00:00:00 BC
(1 row)

    
       SELECT to_timestamp('98','RR');
    to_timestamp     
---------------------
 1998-01-01 00:00:00
(1 row)

    
       SELECT to_timestamp('01','RR');
    to_timestamp     
---------------------
 2001-01-01 00:00:00
(1 row)

to_timestamp(text, text)

Description: Converts values of the string type into the timestamp of the specified type.

Return type: timestamp

Examples:

    
       SELECT to_timestamp('05 Dec 2000', 'DD Mon YYYY');
    to_timestamp
---------------------
 2000-12-05 00:00:00
(1 row)

The following table describes the value formats of the to_number function.

**Table 1** Template patterns for numeric formatting
Schema	Description
9	Value with specified digits
0	Values with leading zeros
Period (.)	Decimal point
Comma (,)	Group (thousand) separator
PR	Negative values in angle brackets
S	Sign anchored to number (uses locale)
L	Currency symbol (uses locale)
D	Decimal point (uses locale)
G	Group separator (uses locale)
MI	Minus sign in the specified position (if the number is less than 0)
PL	Plus sign in the specified position (if the number is greater than 0)
SG	Plus or minus sign in the specified position
RN	Roman numerals (the input values are between 1 and 3999)
TH or th	Ordinal number suffix
V	Shifts specified number of digits (decimal)

Table 2 describes the patterns of date and time values. They can be used for functions to_date, to_timestamp, and to_char, and the nls_timestamp_format parameter.

**Table 2** Schemas for formatting date and time
Type	Schema	Description
Hour	HH	Number of hours in one day (01-12)
	HH12	Number of hours in one day (01-12)
	HH24	Number of hours in one day (00-23)
Minute	MI	Minute (00-59)
Second	SS	Second (00-59)
	FF	Microsecond (000000-999999)
	SSSSS	Second after midnight (0-86399)
Morning and afternoon	AM or A.M.	Morning identifier
Morning and afternoon	PM or P.M.	Afternoon identifier
Year	Y,YYY	Year with comma (with four digits or more)
	SYYYY	Year with four digits BC
	YYYY	Year (with four digits or more)
	YYY	Last three digits of a year
	YY	Last two digits of a year
	Y	Last one digit of a year
	IYYY	ISO year (with four digits or more)
	IYY	Last three digits of an ISO year
	IY	Last two digits of an ISO year
	I	Last one digit of an ISO year
	RR	Last two digits of a year (A year of the 20th century can be stored in the 21st century.) The password must comply with the following rules: If the range of the input two-digit year is between 00 and 49: If the last two digits of the current year are between 00 and 49, the first two digits of the returned year are the same as the first two digits of the current year. If the last two digits of the current year are between 50 and 99, the first two digits of the returned year equal to the first two digits of the current year plus 1. If the range of the input two-digit year is between 50 and 99: If the last two digits of the current year are between 00 and 49, the first two digits of the returned year equal to the first two digits of the current year minus 1. If the last two digits of the current year are between 50 and 99, the first two digits of the returned year are the same as the first two digits of the current year.
	RRRR	Capable of receiving a year with four digits or two digits. If there are 2 digits, the value is the same as the returned value of RR. If there are 4 digits, the value is the same as YYYY.
	BC or B.C. AD or A.D.	Era indicator Before Christ (BC) and After Christ (AD)
Month	MONTH	Full spelling of a month in uppercase (9 characters are filled in if the value is empty.)
	MON	Month in abbreviated format in uppercase (with three characters)
	MM	Month (01-12)
	RM	Month in Roman numerals (I-XII; I=JAN) and uppercase
Day	DAY	Full spelling of a date in uppercase (9 characters are filled in if the value is empty.)
	DY	Day in abbreviated format in uppercase (with three characters)
	DDD	Day in a year (001-366)
	DD	Day in a month (01-31)
	D	Day in a week (1–7. Sunday is 1.)
Week	W	Week in a month (1-5) (The first week starts from the first day of the month.)
	WW	Week in a year (1-53) (The first week starts from the first day of the year.)
	IW	Week in an ISO year (The first Thursday is in the first week.)
Century	CC	Century (with two digits) (The 21st century starts from 2001-01-01.)
Julian date	J	Julian date (starting from January 1 of 4712 BC)
Quarter	Q	Quarter