Oracle -- plsql Composite data type

• Composite variables are also called composite variables. Composite variables include multiple internal components, and each component can store values separately. Therefore, a composite variable can store multiple values.
• The composite variable type is not an existing data type in the database. Therefore, before declaring a composite variable type, you must first create a composite type. The composite type can be used multiple times after being created, to define multiple composite variables. Composite data types include:-record-table-nested table-array record is a logical unit composed of a group of related data items. Each data item has its own name and data type. A table is a collection of data that can be referenced and processed as a whole. A table consists of columns and keywords, and rows can be accessed in groups through keywords. Once defined, record and table can be reused. PL/SQL Records • records are a group of related data items stored in multiple fields. Each field has its own name and data type. • Use a set of fields as a logical unit • It is mainly used to retrieve the queried row data records from a table. Features: • each record can contain many fields. • You can assign initial values to records, at the same time, not null can be used to limit Records • fields without initial values are defined as NULL • reserved words DEFAULT can also be used when defining fields • RECORD can be defined in the Declaration part of any block, subroutine or package type and declare User-Defined Records • can declare and reference nested records, a record can be a component Syntax of other records: [plain] TYPE type_name is record (field_declaration [, field_declaration]…); Field_declaration: [plain] field_name {field_type | variable % TYPE | table. column % TYPE | table % ROWTYPE} [[not null] {: = | DEFAULT} expr] [plain] TYPE emp_record_type is record (empno emp. empno % type, ename emp. ename % type, job varchar2 (9); emp_record emp_record_type; you can use the point number to reference the record_name.field_name % ROWTYPE attribute in the record. • The declared variables correspond to the set of columns in the database table or view. • Add the database table name before % ROWTYPE • field in the record for the name and data type, refer to [plain] DECLARE emp in the table or view. _ Record emp % rowtype ;.... Emp_record.ename = 'ljs'; emp_record.sal = 3000; SELECT * INTO emp_record FROM emp WHERE ......; Advantages of % ROWTYPE: • you do not need to know the number and type of columns in the database. • During running, the number and type of columns in the database may change. • This attribute can be used in SELECT statements to effectively retrieve rows in a TABLE and create PL/SQL tables [plain] TYPE type_name IS table OF {column_type | variable % TYPE | TABLE. column % TYPE} [not null] [index by BINARY_INTEGER]; identifier type_name; [plain] declare type ename_table_type is table of emp. ename % type index by BINARY_INTEGER; TYPE partition is table of date index by BINARY_INTEGER; ename_table ename_table_type; hiredate_table partition; BEGIN ename_table (1): = 'cameron '; hiredate_table (8 ): = SYSDATE + 7; IF ename_table.EXISTS (1) then insert ...... END; table method:
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