How Oracle implements random reading of values from a specific combination

Here, we will use the Dbms_random package and case when statement, the idea is as follows:

First, the use of dbms_random. The random function randomly generates values and then models the values, and if we want to read them randomly in 10 elements, we need to take a modulo of 10.

Secondly, the value after modulo is associated with the element using the case when statement.

For example, I have a combination of "Beijing", "Shanghai", "Guangzhou", "Shenzhen", "Wuhan" Five elements that want to randomly read values from these five elements to populate a field of the table.

First, create a test table

SQL>createtablevarchar2(2char)); Table created.

Constructs an SQL statement that can read elements randomly

Select  CaseMoDABS(Dbms_random.random),5)        when 1  Then 'Beijing'        when 2  Then 'Shanghai'        when 3  Then 'Guangzhou'        when 4  Then 'Shenzhen'       Else 'Wuhan' End"LOC" fromDual

Loc field for bulk fill test table

begin   forIinch 1..TenLoopInsert  intoTestValues( CaseMoDABS(Dbms_random.random),5)           when 1  Then 'Beijing'           when 2  Then 'Shanghai'           when 3  Then 'Guangzhou'           when 4  Then 'Shenzhen'          Else 'Wuhan' End ); EndLoop;End;

The results of the final generation are as follows:

SQL>Select* from test; LOC-------- Wuhan Guangzhou Shanghai Beijing Shanghai Wuhan Beijing Shanghai Wuhan Shenzhen  the rows selected.

How Oracle implements random reading of values from a specific combination