How to convert Oracle data types

Oracle data type conversion method: 1. Use the cast() function, the syntax "cast(x as type)"; 2. Use the to_char() function, the syntax "to_char(x[,f])" ;3. Use to_date() function, syntax "to_date(x[,f])", etc.

The operating environment of this tutorial: Windows 7 system, Oracle 11g version, Dell G3 computer.

oracle’s data type conversion method

1. Use cast()

cast( ) is a data type conversion function. This function can convert x to the corresponding data type. It is basically used for numeric, character, and time types to install database rules for mutual conversion.

Syntax:

cast(x as type)

Example:

select 
 cast('123' as number) num,cast(123 as varchar2(3)) as ch,cast(to_date('20211112','yyyymmdd') as varchar2(12)) as time
from dual;

Result:

123
'123'
12-11月-21

2. Use to_char()

The to_char() function can format a string or time type x into a string according to format f.

Syntax:

to_char(x[,f])

Example:

select to_char(123.46,'999.9') from dual;
select to_char(sysdate,'yyyy-mm-dd') from dual;

Result:

 123.5
2021-11-13

3. Use to_date()

The to_date() function can format the string x according to format f and convert it into a time type result.

Syntax:

to_date(x[,f])

Example:

select to_date('2021-11-13','yyyy-mm-dd') from dual;

Result:

2021/11/13

4. Use to_number()

The to_number() function can format the string x according to format f and convert it into a numerical type result.

Grammar:

to_number(x[,f])

Example:

select to_number('123.74','999.99') from dual

Result:

123.74

Description: For the format f of the value, please refer to the following table

##99,9##$##Recommended tutorial: "Oracle Tutorial

Parameters	##Example	illustrate
9	##999	Return the number at the specified position
.	99.9	Specify the position of the decimal point
,	##Returns a comma at the specified position
	$99.9	## Returns a dollar sign at the beginning
EEEE	##9.99EEEE	Specify scientific notation

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