研究Oracle中动态SQL语句太长的问题

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> declare
2 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 begin
7 l_stmt(1) := 'select 1 c1';
8 for i in 2 .. 15000
9 loop
10 l_stmt(i) := ', 1 c' || i;
11 end loop;
12 l_stmt(15000) := 'from dual';
13 for i in l_stmt.first .. l_stmt.last
14 loop
15 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.sql
select 1 c1
, 1 c2
...........................

SQL> host tail longSQL.sql
................
, 1 c14999
, 1 c15000
from 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 , 1
c11 , 1 c12 , 1 c13 , 1 c14 , 1 c15 , 1 c16 , 1 c17 , 1 c18 , 1 c19 , 1 , 1 .............................................................................................
1978774 780448 241252