Type Conversion Functions

Type Conversion Functions

• cast(x as y)

  Description: Converts x into the type specified by y.

  For example:

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

• hextoraw(string)

  Description: Converts a string in hexadecimal format into binary format.

  Return type: raw

  For example:

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  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

  For example:

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

• pg_systimestamp()

  Description: Obtains the system timestamp.

  Return type: timestamp with time zone

  For example:

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

• rawtohex(string)

  Description: Converts a string in binary format into hexadecimal format.

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

  Return type: varchar

  For example:

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  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, MM, SS, YYYY, MM, and DD. For details, see Table 2.
  • 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

  For example:

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

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  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

  For example:

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  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 includes 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 (.). For details, see Table 1.
  • 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

  For example:

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

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

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

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  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

  For example:

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  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

  For example:

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  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

  For example:

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  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

  For example:

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  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

  For example:

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  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

  For example:

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

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

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

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

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

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

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  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

  For example:

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  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

  For example:

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  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. For details about the fmt format, see Table 2.

  This function cannot support the CLOB type directly. However, a parameter of the CLOB type can be converted using implicit conversion.

  Return type: date

  For example:

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  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

  For example:

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  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

  For example:

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  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

  For example:

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  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. For details about the fmt format, see Table 2.

  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

  For example:

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  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)

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  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)

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

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

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  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

  For example:

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  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.