Oracle single row Functions

Single-row functions are mainly divided into five types: The varchar2 function, the number function, and the date function, Common functions, Conversion functions

Character FunctionsThe main function is to operate string data, such:

. Upper (string and column): converts the input string to uppercase and returns the result;

. Lower (string and column): converts the input string to lowercase and returns the result;

. Initcap (string and column): upper-case letters at the beginning;

. Length (string, column): returns the length of the string;

. Replace (string, column): replace;

. Substr (string, column, start point [, end point]): String truncation;

Numeric FunctionsFor example:

. Round (number and column [number of digits retained]): rounding operation;

. Trunc (number and column): discard content at the specified position;

. Mod (number 1, number 2); modulo and remainder

Date Functions

Get current date: sysdate

select  sysdate  from dual;

. Last_day ()

. Next_dat (date, number of weeks)

. Add_months (date, number)

. Months_between (date 1, date 2)

Conversion functions

. To_char (string | column, Format String): converts a date or number to a string for display.

. To_date (string, Format String); Convert string to date data display

. To_number (string): converts a string to a number for display.

select TO_CHAR(sysdate,'yyyy-mm-dd'),TO_CHAR(sysdate,'yyyy') from dual

select TO_CHAR(sysdate,'fmyyyy-mm-dd'),TO_CHAR(sysdate,'yyyy') from dual

Remove the leading 0 of the date;

select TO_CHAR(sysdate,'hh24'),TO_CHAR(sysdate,'hh-mi-ss') from dual

Number formatting

select TO_CHAR(1222223,'999,999,999') from dual

Currency

select TO_CHAR(1222223,'L999,999,999') from dual

L (locale) Currency symbols in the current language environment

Common functionsFor example:

. Nvl () function, processing null

select NVL(money,0)  from demo;

. Decode () function: multi-value judgment

Decode (column, judgment value 1, display value 1, judgment value 2, display value 2)