what is context switching in pl sql?
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SQL statements are called from PL/SQL in a loop, so the execution will switch back and forth between the PL/SQL engine and the SQL engine. This switch between two environments is known as a context switch. Context switches increase elapsed time of your programs and introduce unnecessary CPU overhead.
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Here is the syntax for the WHILE loop statement: WHILE condition LOOP statements; END LOOP; The condition in the WHILE is a Boolean expression that evaluates to TRUE , FALSE or NULL . ... PL/SQL evaluates the condition in the WHILE clause before each loop iteration.
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['Scalar Functions (Returns A Single Value)', 'Inline Table Valued Functions (Contains a single TSQL statement and returns a Table Set)', 'Multi-Statement Table Valued Functions (Contains multiple TSQL statements and returns Table Set)']
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To open a cursor, you use the following syntax: OPEN cursor_name; In this syntax, the cursor_name is the name of the cursor declared in the declaration section. When you open a cursor, Oracle parses the query, binds variables, and executes the associated SQL statement.
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PL/SQL Raise Exception. All the predefined exceptions are raised implicitly whenever the error occurs. But the user-defined exceptions needs to be raised explicitly. ... If 'RAISE' is used separately in the program, then it will propagate the already raised exception to the parent block.
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DDL commands are not allowed as PL/SQL constructs in PL/SQL blocks. Using DBMS_SQL or EXECUTE IMMEDIATE, we can execute create table, drop, alter, analyze, truncate and other DDL's too. PL/SQL PROCEDURE successfully completed.
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UPDATE test SET test1 = NVL(test1, 'hello'), test2 = NVL(test2, 'world') WHERE test2 IS NULL OR test1 IS NULL; Though it may fire your update triggers even for the rows that are effectively unchanged. COALESCE() works similarly to NVL() in this circumstance -- returning the first non-null value.
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The WHILE loop statement continues to execute the statements between the LOOP and END LOOP as long as the condition in the WHILE clause evaluates to TRUE . PL/SQL evaluates the condition in the WHILE clause before each loop iteration. If the condition is TRUE , then the loop body executes.
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['2.1 Use Prepared Statement. ... ', '2.2 Use Connection Pool. ... ', '2.3 Disable Auto Commit Mode. ... ', '2.4 Use JDBC Batch Statements. ... ', '2.5 Accessing Result Set by Column Names. ... ', '2.6 Use Bind variables instead of String Concatenation.']
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The point of context switching is to allow several clients to access the card at the same time, without bad hardware level interference. ... This means that, until all channels are used, each graphics client will have its own channel and hardware context on the card.
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Context Switch Definition. A context switch (also sometimes referred to as a process switch or a task switch) is the switching of the CPU (central processing unit) from one process or thread to another. A process (also sometimes referred to as a task) is an executing (i.e., running) instance of a program.
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Context switching is the technique where CPU time is shared across all running processes and processor allocation is switched in a time bound fashion. To schedule a process to allocate the CPU, a running process is interrupted to a halt and its state is saved.
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Scheduling and Context Switching. ... Context Switching, which consists of stopping one process and starting a new one. Scheduling, which consists of choosing a new process among the processes that are eligible for execution.
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DDL statements are not allowed in Procedures (PLSQL BLOCK) PL/SQL objects are precompiled. ... On the other hand, DDL (Data Definition Language) statements like CREATE, DROP, ALTER commands and DCL (Data Control Language) statements like GRANT, REVOKE can change the dependencies during the execution of the program.
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1-Bind parameters are used to replace a single value in SQL or PL/SQL, such as a character string, number, or date. 2-Lexical parameters are placeholders for text that you embed in a SELECT statement. Use Lexical reference when you want the parameter to substitute multiple values at runtime.
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A synchronous Oracle change data capture is implemented using triggers that inserts entries to a change-table every time a data modification operation is executed. Triggers are hooks that get executed as part of the transactions.
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You can use DML inside a PL/SQL function - no problem. However, the function can only be called from PL/SQL, not from SQL - i.e. it can be called like this: ... Many people (including me) don't like functions that have "side effects" like this, but that is a matter of best practice and standards, not a technical issue.