Memory Table in PLSQL-- Index By Table
In fact, a memory table is a bit like an array in java, but it is more powerful than an array.
1. First of all, let's briefly introduce the role of memory tables:
An index primary key made up of BINARY_INTEGER types
Fields of simple types or user-defined types as specific array elements
two。 How to use memory table types?
Define memory table types
TYPE type_name IS TABLE OF storage type (number, employees.last_name%TYPE, employees%ROWTYPE, varchar2)
INDEX BY (BINARY_INTEGER,varchar2 (80)..)
-varchar2 (80) indicates that subscripts can be accessed through strings, which is more powerful than arrays in java
Declare a variable of this type
Identifier type_name
3. Some properties and methods in memory table
Assignment:
Identifier (1): = 'Jams'-- this is index by binary_integer
Identifier ('A'): = 'Jams'-- this is index by varchar2
Unlike arrays in java, memory tables can use strings as subscript
3-1.count method:
Identifier.count-returns the number of rows in the memory table
3-2.exists method:
Identifier.exists (1)-determines whether an element with subscript 1 exists
3-3.first and last attributes:
First: the index that returns the first row
Last: returns the index of the last row
The usage of first and last:
Generally used in the case of traversing memory tables
For i in identifier.first.. Identifier.last loop .end loop
Two points must be noted here:
1. If there is no data in the memory table, but you traverse it in this way, you will report an error, so you should use the
Count method to make a judgment.
two。 What if the data subscript in the memory table is not contiguous?
For example, there are only identifier (2) and identifier (5) in memory tables.
When traversing to the subscript 1, 4, do exception or error handling, otherwise the error will be reported.
3-4.delete method:
Identifier.delete (1)-deletes the element with subscript 1 in the memory table
Identifier.delete-deletes all elements of the memory table
3-5.next and prior attributes:
Identifier.next (1)-returns the next row index in the memory table with subscript 1
Identifier.prior (2)-returns the index of the previous row in the memory table with a subscript of 2 rows
The function of INDEX BY BINARY_INTEGER is attached here.
-- http://blog.itpub.net/26690043/viewspace-722081/
