经典的print_table学习

存储过程接受两个参数:SQL语句和日期,还使存储过程可以使用role 权限

create or replace procedure print_table(p_query in varchar2,p_date_fmt in varchar2 default ‘DD-MM-YY HH24:MI:SS‘)-- this utility is designed to be installed ONCE in a database and used-- by all. Also, it is nice to have roles enabled so that queries by-- DBA‘s that use a role to gain access to the DBA_* views still work-- that is the purpose of AUTHID CURRENT_USERAUTHID CURRENT_USER --存储过程可以使用role权限is l_theCursor integer default dbms_sql.open_cursor; l_columnValue varchar2(4000); l_status integer; l_descTbl dbms_sql.desc_tab; l_colCnt number; l_cs varchar2(255); l_date_fmt varchar2(255);

定义了一个子存储过程restore，用于脚本执行完成恢复配置(cursor_sharing、nls_date_format)，以及关闭游标。

-- small inline procedure to restore the sessions state-- we may have modified the cursor sharing and nls date format-- session variables, this just restores themprocedure restore isbegin if (upper(l_cs) not in ( ‘FORCE‘,‘SIMILAR‘ )) then execute immediate ‘alter session set cursor_sharing=exact‘; end if; if ( p_date_fmt is not null ) then execute immediate ‘alter session set nls_date_format=‘‘‘ || l_date_fmt || ‘‘‘‘; end if; dbms_sql.close_cursor(l_theCursor);end restore;

若输入参数p_date_fmt不为空，存储系统默认的nls_date_format，用于restore

begin-- I like to see the dates print out with times, by default, the-- format mask I use includes that. In order to be "friendly"-- we save the date current sessions date format and then use-- the one with the date and time. Passing in NULL will cause-- this routine just to use the current date formatif ( p_date_fmt is not null )then select sys_context( ‘userenv‘, ‘nls_date_format‘ ) into l_date_fmt from dual; execute immediate ‘alter session set nls_date_format=‘‘‘ || p_date_fmt || ‘‘‘‘;end if;

为了让这个存储过程，执行的SQL语句能用上绑定变量，减小硬解析，设置cursor_sharing为FORCE，

-- to be bind variable friendly on this ad-hoc queries, we-- look to see if cursor sharing is already set to FORCE or similar, if not, set it so when we parse -- literals are replaced with bindsif (dbms_utility.get_parameter_value( ‘cursor_sharing‘, l_status, l_cs ) = 1 )then if ( upper(l_cs) not in (‘FORCE‘,‘SIMILAR‘)) then execute immediate ‘alter session set cursor_sharing=force‘; end if;end if;

解析和描述SQL语句原文，逐字段来定义(113是BLOB类型此处不适用)，所有的字段全部转换为string .按照4000字节定义，

-- parse and describe the query sent to us. we need to know the number of columns and their names.dbms_sql.parse(l_theCursor, p_query, dbms_sql.native );dbms_sql.describe_columns( l_theCursor, l_colCnt, l_descTbl );-- define all columns to be cast to varchar2‘s, we are just printing them outfor i in 1 .. l_colCnt loop if ( l_descTbl(i).col_type not in ( 113 ) ) then dbms_sql.define_column(l_theCursor, i, l_columnValue, 4000); end if;end loop;

逐字段打印每一列，因为dbms_output仅打印255个字符/行，因此此处列显示200个字符截取了，同时列名右补空格满足30位，

-- execute the query, so we can fetchl_status := dbms_sql.execute(l_theCursor);-- loop and print out each column on a separate line-- bear in mind that dbms_output only prints 255 characters/line-- so we‘ll only see the first 200 characters by my design...while ( dbms_sql.fetch_rows(l_theCursor) > 0 )loop for i in 1 .. l_colCnt loop if ( l_descTbl(i).col_type not in ( 113 ) ) then dbms_sql.column_value( l_theCursor, i, l_columnValue ); dbms_output.put_line( rpad( l_descTbl(i).col_name, 30 )|| ‘: ‘ ||substr( l_columnValue, 1, 300 ) ); end if; end loop; dbms_output.put_line( ‘-----------------‘ );end loop;

执行完成/出现异常时调用了restore

-- now, restore the session state, no matter whatrestore;exception when others then restore;raise;end;/

refer to :https://asktom.oracle.com/pls/apex/f?p=100:11:0::::P11_QUESTION_ID:1035431863958