例如在java中,通过prepareStatement,每个session对该sql prepare一次,而不是每次调用都prepare一次。 2. PLSQL自动cache cursor 在PLSQL中,所有static sql都是被cache的,重复调用时不会进行soft parse。注意动态sql除外。 declareinumber; jnumber; knumber;begini:=1; k:=12345678;whilei<=10000loopselectcount(*...
2. Sql的执行过程和parse分类,oracle运行sql时,过程如下: (1). Sql cursor是否open?如果是则跳到5) 这种情况即为no parse,为方便比较,我们也作为parse的一种类型 (2). cursor是否在session cache中(pga),如果存在,则跳到5)这种情况oracle专家tom称其softer soft parse (3). 进行syntax check和 semantic che...
1CREATEORREPLACEPACKAGE panel_period_pkgAS2TYPE ppidtabletype IS TABLE OF NUMBER;--PL/SQL集合,非SQL中可见3FUNCTIONalloc_to_dp(p_strINVARCHAR2,4p_display_period_idINNUMBER,5p_user_idINVARCHAR2)RETURNVARCHAR2;6FUNCTIONcreate_ppa_list_from_string(p_strINVARCHAR2)7RETURNppidtabletype;8ENDpanel_pe...
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 ...
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 ...
If Oracle bind variables are used, however, the TKPROF output is more helpful. For example: INSERT INTO TABLE (A, B, C) VALUES ( :a1, :a2, :a3) call count cpu elapsed disk query current rows --- --- --- --- --- --- --- --- Parse 687 0.01 0.01 0 0 0 0 Execute 687...
使用concat函数连接字符串,在MySQL中,这个函数支持多个参数,但是在Oracle中只支持两个参数。 由于不同数据库之间的语法差异,如果更换了数据库,有些SQL语句可能就需要重写。 针对这种情况,可以使用bind标签来避免由于更换数据库带来的一些麻烦。 我们将上面的语句改为bind方式,如下 代码语言:javascript 代码运行次数:0 运...
Oracle 是支持数组处理功能的数据源的示例。 实现此功能的另一种方法是让驱动程序生成一批 SQL 语句,为参数数组中的每个参数集生成一个 SQL 语句,并执行批处理。 参数数组不能与 UPDATE WHERE CURRENT OF语句一起使用。 处理参数数组时,单个结果集/行计数(每个参数集各有一个)可用,或者结果集/行计数可以汇总为一...
Oracle introduced a new feature called adaptive cursor sharing (ACS) in Oracle Database 11g, to improve the plans that are selected for queries containing bind variables. This feature can result in more cursors for the same query containing bind variable
V$SQL_BIND_CAPTUREdisplays information on bind variables used by SQL cursors. Each row in the view contains information for one bind variable defined in a cursor. This includes: Reference to the cursor defining the bind variable (hash_value,address) for the parent cursor and (hash_value,child...