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Programmers can use them anywhere in a SQL or PL/SQL statement or in SQL Plus commands. They can be populated by a literal using DEFINE or from the database using the column command. predefined variables, prefixed with an underscore ('_') [10] substitution variables, useful for interacting with user-input [11] bind variables, prefixed by a ...
Transact-SQL (T-SQL) is Microsoft's and Sybase's proprietary extension to the SQL (Structured Query Language) used to interact with relational databases.T-SQL expands on the SQL standard to include procedural programming, local variables, various support functions for string processing, date processing, mathematics, etc. and changes to the DELETE and UPDATE statements.
The scope of local variables is determined by using the 'new' command to declare the variable. Declaration is optional - an undeclared variable is in scope for all routines running in the same process. A declared variable is accessible at the stack level it was declared, and remains accessible as long as that stack level exists. This means that ...
SQL includes operators and functions for calculating values on stored values. SQL allows the use of expressions in the select list to project data, as in the following example, which returns a list of books that cost more than 100.00 with an additional sales_tax column containing a sales tax figure calculated at 6% of the price.
PL/SQL includes procedural language elements such as conditions and loops, and can handle exceptions (run-time errors). It allows the declaration of constants and variables, procedures, functions, packages, types and variables of those types, and triggers. Arrays are supported involving the use of PL
Major DBMSs, including SQLite, [5] MySQL, [6] Oracle, [7] IBM Db2, [8] Microsoft SQL Server [9] and PostgreSQL [10] support prepared statements. Prepared statements are normally executed through a non-SQL binary protocol for efficiency and protection from SQL injection, but with some DBMSs such as MySQL prepared statements are also available using a SQL syntax for debugging purposes.
Thus, editing a global variable is making permanent and immediate changes to a system-universal database (which survives reboots, etc.). The scope of a private variable is the local function, the scope of a public variable is the entire process. Variables, private and public, may be single elements or complete multi-dimensional arrays.
Stored procedure parameters will be treated as data even if an attacker inserts SQL commands. Also, some DBMS will check the parameter's type. However, a stored procedure that in turn generates dynamic SQL using the input is still vulnerable to SQL injections unless proper precautions are taken.