Whena query uses literals, the optimizer can use theliteral values to find the best plan. However, when a query uses bindvariables, the optimizer must select the best plan without the presence ofliterals in the SQL text. This task can be extremely difficult. By peeking at bind values the ...
一、绑定变量用法和使用场合 使用绑定变量的重要性:如果不使用绑定变量而使用常量,会导致大量硬解析。由于硬解析的种种危害,不使用绑定变量往往是影响oracle性能和扩展性的最大问题 以下为一些错误写法和正确写法的例子 1. PLSQL中普通查询 (1). 错误写法 SELECT * FROM emp WHERE empno=123; (2). 正确写法(未...
二、如何判断和定位系统中未使用绑定变量的语句 在awr的load profile部分,有个Hard parses指标,表示每秒的hard parse。 另外在Instance Efficiency Percentages部分,Soft Parse %这个指标反映的是硬解析占所有解析的比例。 这两个指标一个是绝对值,一个是相对值。每秒hard parse指标应该比较低,而soft parse%应该较...
To demonstrate using bound variables, a real-world example is best. The application in question, which I worked on some years ago, allowed golf professionals to establish what tee times were available at their golf course and at what price. For example, they might say that on a particular S...
with bind variables, if it is safe to do so. This is controlled with the CURSOR_SHARING startup parameter. The CURSOR_SHARING_EXACT hint causes this behavior to be switched off. In other words, Oracle executes the SQL statement without any attempt to replace literals by bind variables. ...
Regardless of the batch value of an Oracle prepared statement, if any of the bind variables of the statement is (or becomes) a streaming type, then JDBC sets the batch value to 1 and sends any queued requests to the database for execution. ...
The Oracle JDBC driver supports bind variables of type REFCURSOR. A REFCURSOR is represented by a JDBC ResultSet. Use the getCursor method of the CallableStatement to convert a REFCURSOR value returned by a PL/SQL block into a ResultSet. JDBC lets you call a stored procedure that executes a ...
A bind variable identifier always begins with a single colon ( :). SELECT department_name FROM departments WHERE department_id = :department_id Note that bind variables can also be used with UPDATE, INSERT, and DELETE statements, and also with stored procedures. The following code illustrates ...
Execute a SQL SELECT query with the table name as a dynamic variable using bind variables. This query returns the number of employees under a manager with a specific ID. DO $$DECLARE Tabname varchar(30) := 'employees'; num integer := 1; cnt integer; BEGIN EXECUTE format('S...
The Oracle update batching model allows you to "batch" multiple executions of a single statement with different bind variables. Actual execution happens when the number of batched executions reaches the "batch value", which is set by this method. The batch value for this prepared statement can...