研究Oracle中动态SQL语句太长的问题

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研究Oracle中动态SQL语句太长的问题

2024-07-09 20:59| 来源: 网络整理| 查看: 265

SQL语句太长了,需要通过dbms_sql.varchar2s这个数组类型来进行存储。然后才能执行。declare    l_stmt dbms_sql.varchar2s;    l_cursor integer default dbms_sql.open_cursor;    l_rows number default 0;    l_length number := 0;begin    l_stmt(1) := 'select 1 c1';    for i in 2 .. 15000 loop        l_stmt(i) := ', 1 c' || i;    end loop;    l_stmt(15000) := 'from dual';    for i in l_stmt.first .. l_stmt.last    loop        l_length := l_length + length(l_stmt(i));    end loop;    dbms_output.put_line( 'length = ' || l_length );    dbms_sql.parse( c => l_cursor,    statement => l_stmt,    lb => l_stmt.first,    ub => l_stmt.last,    lfflg => TRUE,    language_flag => dbms_sql.native );    l_rows := dbms_sql.execute(l_cursor);    dbms_sql.close_cursor( l_cursor );end;/以下参考:http://www.stcore.com/html/2006/0307/114096.html

最近遇见一个ORA-01795: maximum number of expressions in a list is 1000 错误,才知道In-list有1000个元素的限制;可以使用array bind或者temporary table解决,而且还能绑定变量。[Limit and conversion very long IN list : WHERE x IN ( ,,, ...) ]

再想到SQL的长度是否在SQLPLUS里面还有其他的限制?

Logical Database Limits

SQL Statement Length Maximum length of statements 64 K maximum; particular tools may impose lower limits

9i的文档写的最大64K,其实不正确。

在10g的文档中作了修改 Logical Database Limits

The limit on how long a SQL statement can be depends on many factors, including database configuration, disk space, and memory

仔细想想,我们数据库中 package 几十K有很多,当初都是用sqlplus执行创建的;sqlpplus对日常执行的SQL因该不会有长度限制。

先测试一下使用DBMS_SQL执行很长的SQL语句。

SQL> declare2 l_stmt dbms_sql.varchar2s;l_cursor integer default dbms_sql.open_cursor;l_rows number default 0;3 4 5 l_length number := 0;6 begin7 l_stmt(1) := 'select 1 c1';8 for i in 2 .. 150009 loop10 l_stmt(i) := ', 1 c' || i;11 end loop;12 l_stmt(15000) := 'from dual';13 for i in l_stmt.first .. l_stmt.last14 loop15 l_length := l_length + length(l_stmt(i));16 end loop;17 dbms_output.put_line( 'length = ' || l_length );18 dbms_sql.parse( c => l_cursor,19 statement => l_stmt,20 lb => l_stmt.first,21 ub => l_stmt.last,22 lfflg => TRUE,23 language_flag => dbms_sql.native );25 l_rows := dbms_sql.execute(l_cursor);26 dbms_sql.close_cursor( l_cursor );27 end;28 /length = 138898

PL/SQL procedure successfully completed.

通过dbms_sql.varchar2s数组,可以执行很长的SQL。

再将如上pl/sql产生的SQL使用dbms_output输出longSQL.sql.

SQL> host ls -l longSQL.sql-rw-r--r-- 1 oracle dba 1215082 Dec 4 05:19 longSQL.sql

SQL> host head longSQL.sqlselect 1 c1, 1 c2...........................

SQL> host tail longSQL.sql................, 1 c14999, 1 c15000from dual;

这个1M的SQL在sqlplus里完全可以执行。看来,oracle完全支持很长的SQL语句;但该sql会占用很多share pool空间,因此不提倡经常执行。

SQL> select sql_text, SHARABLE_MEM,PERSISTENT_MEM,RUNTIME_MEM from v$sql where sql_text like '%, 1 c2%';

SQL_TEXT--------------------------------------------------------------------------SHARABLE_MEM PERSISTENT_MEM RUNTIME_MEM------------ -------------- -----------select 1 c1 , 1 c2 , 1 c3 , 1 c4 , 1 c5 , 1 c6 , 1 c7 , 1 c8 , 1 c9 , 1 c10 , 1c11 , 1 c12 , 1 c13 , 1 c14 , 1 c15 , 1 c16 , 1 c17 , 1 c18 , 1 c19 , 1 , 1 .............................................................................................1978774 780448 241252



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