tailieunhanh - HandBooks Professional Java-C-Scrip-SQL part 168

Tham khảo tài liệu 'handbooks professional java-c-scrip-sql part 168', công nghệ thông tin, kỹ thuật lập trình phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Variables and Program Data PL SQL programs are normally used to manipulate database information. You commonly do this by declaring variables and data structures in your programs and then working with that PL SQL-specific data. A variable is a named instantiation of a data structure declared in a PL SQL block either locally or in a package . Unless you declare a variable as a CONSTANT its value can be changed at any time in your program. The following table summarizes the different types of program data Type Description Scalar Variables made up of a single value such as a number date or Boolean Composite Variables made up of multiple values such as a record or a collection Reference Pointers to values LOB Variables containing large object LOB locators Scalar Datatypes Scalar datatypes divide into four families number character datetime and Boolean. Numeric datatypes Numeric datatypes are further divided into decimal binary integer and PLS_INTEGER storage types. Decimal numeric datatypes store fixed and floating-point numbers of just about any size. They include NUMBER DEC DECIMAL NUMERIC FLOAT REAL and DOUBLE PRECISION. The maximum precision of a variable with type NUMBER is 38 digits which yields a range of values from through . This range of numbers would include the mass of an electron over the mass of the universe or the size of the universe in angstroms. Variables of type NUMBER can be declared with precision and scale as follows NUMBER recz szow scale where precision is the number of digits and scale is the number of digits to the right positive scale or left negative scale of the decimal point at which rounding occurs. Legal values for scale range from -84 to 127. The following table shows examples of precision and scale Declaration Assigned value Stored value NUMBER NUMBER 4 8675 8675 NUMBER 4 8675309 Error NUMBER 12 5 NUMBER 12 -5 8675309 8700000 Binary integer numeric datatypes store whole .