TAILIEUCHUNG - Oracle PLSQL Language- P8

Tham khảo tài liệu 'oracle plsql language- p8', công nghệ thông tin, cơ sở dữ liệu phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | exception weensy_plus Lots of room for me to type now When you create a subtype based on an existing variable or database column that subtype inherits the length or precision and scale in the case of a NUMBER datatype from the original datatype. This constraint takes effect when you declare variables based on the subtype but only as a default. You can always override that constraint. You will have to wait for a future version of PL SQL however to actually enforce the constraint in a programmer-defined subtype. Finally an anchored subtype does not carry over the NOT NULL constraint to the variables it defines. Nor does it transfer a default value that was included in the original declaration of a variable or column specification. Previous Anchored Declarations Oracle PL SQL Programming 2nd Edition Next Tips for Creating and Using Variables Anchored Declarations Book Index Tips for Creating and Using Variables The Oracle Library Navigation Copyright c 2000 O Reilly Associates. All rights reserved. Please purchase PDF Split-Merge on to remove this watermark. Chapter 4 Previous Variable Declarations Variables and Program Data Next Programmer-Defined Subtypes Anchored Declarations This section describes the use of the TYPE declaration attribute to anchor the datatype of one variable to another data structure such as a PL SQL variable or a column in a table. When you anchor a datatype you tell PL SQL to set the datatype of one variable from the datatype of another element. The syntax for an anchored datatype is variable name type attribute TYPE optional default value assignment where variable name is the name of the variable you are declaring and type attribute is any of the following Previously declared PL SQL variable name Table column in format Figure shows how the datatype is drawn both from a database table and PL SQL variable. Figure Anchored declarations with TYPE DECLARE emp_ld TYPE .

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