Round () function, null value in Oracle, RowNum

Round () Function: Rounding function

Returns a numeric value that is the result of rounding operations with the specified precision.

Syntax: Round (number[,decimals])

Number: The function to be processed

Decimals: Precision, default is 0;

Select round (123.456,0) as A,round (123.456,1) as B,round (123.456,-1) as C from dual;

Null value:

A null value is no value or missing value. A column that allows null values also allows the column's value to be not given when the row is inserted. Columns that do not allow null values do not accept rows with no values for the column, in other words, the column must have a value when the row is inserted or updated.

Each table column is either a null value or a NOT NULL column, which is created with a table definition, such as:

CREATE TABLE Orders (  order_num  INTEGER not  null,  order_date DATETIME not NULL,  order_id   CHAR (ten) not NULL);

The above statement creates a table with 3 fields, each of which is qualified by the keyword NOT null, so inserting a column with no value will return an error and insert failed.

RowNum

RowNum can only be used for < If you want to use it, you can use the two methods to achieve:

With Row_number () over ():

Select Areaid from        (select Areaid, Row_number () over (order by Areaid) T from        Cumenu) K         where T > 5;

Instantiation:

Select Areaid from        (select Areaid, RowNum r from          cumenu)         where r > 5;

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Round () function, null value in Oracle, RowNum