ORACLE PL/SQL 为每个传递表名到过程 [英] ORACLE PL/SQL for each passing tablename to procedure

问题描述

我需要在过程中执行 FOR EACH 循环，但我需要动态传递表名.

I need to do a FOR EACH loop in a procedure, but I need to pass the table name dynamically.

这是声明

CREATE OR REPLACE PROCEDURE MIGRATE_PRIMITIVES_PROPS
(
    FromTable IN VARCHAR2, 
    ToTable IN VARCHAR2
)

当我尝试这样做时FOR EachRow IN (SELECT * FROM FromTable) 它说表格无效

When I try and do this FOR EachRow IN (SELECT * FROM FromTable) It says the table isn't valid

进入程序的表是动态的，列一直在添加和删除，所以我无法拼出列并使用游标来填充它们.

The table coming into the procedure is dynamic, columns are added and deleted all the time so I can't spell out the columns and use a cursor to populate them.

推荐答案

您必须使用动态 SQL 来查询您在编译时不知道名称的表.您可以使用动态游标来做到这一点:

You have to use dynamic SQL to query a table whose name you don't know at compile time. You can do that with a dynamic cursor:

as
    l_cursor sys_refcursor;
begin
    open l_cursor for 'select * from ' || fromtable;
    loop
      fetch l_cursor into ... 

...但随后它崩溃了，因为您无法定义记录类型以根据弱引用游标获取/a>;并且您不知道您真正感兴趣的列名称或类型 - 您正在使用 select * 并且有特定名称要排除，不包括.您提到了一个可以工作并获取列名的内部循环，但是在该游标中无法引用字段也可以动态变量.

... but then it breaks down because you can't define a record type to fetch into based on a weak ref cursor; and you don't know the column names or types you're actually interested in - you're using select * and have specific names to exclude, not include. You mentioned an inner loop that works and gets the column names, but there is no way to refer to a field in that cursor variable dynamically either.

所以你必须更加努力地工作并使用 dbms_sql 包，而不是本地动态 SQL.

So you have to work a bit harder and use the dbms_sql package instead of native dynamic SQL.

这是一个基本版本:

create or replace procedure migrate_primitives_props
(
    fromtable in varchar2, 
    totable in varchar2
)
as
    l_cursor pls_integer;
    l_desc_tab dbms_sql.desc_tab;
    l_columns pls_integer;
    l_value varchar2(4000);
    l_status pls_integer;
begin
    l_cursor := dbms_sql.open_cursor;

    -- parse the query using the parameter table name
    dbms_sql.parse(l_cursor, 'select * from ' || fromtable, dbms_sql.native);
    dbms_sql.describe_columns(l_cursor, l_columns, l_desc_tab);

    -- define all of the columns
    for i in 1..l_columns loop
        dbms_sql.define_column(l_cursor, i, l_value, 4000);
    end loop;

    -- execute the cursor query
    l_status := dbms_sql.execute(l_cursor);

    -- loop over the rows in the result set
    while (dbms_sql.fetch_rows(l_cursor) > 0) loop
        -- loop over the columns in each row
        for i in 1..l_columns loop
            -- skip the columns you aren't interested in
            if l_desc_tab(i).col_name in ('COL_NAME', 'LIB_NAME', 'PARTNAME',
                'PRIMITIVE', 'PART_ROW')
            then
                continue;
            end if;

            -- get the column value for this row
            dbms_sql.column_value(l_cursor, i, l_value);
            -- insert the key-value pair for this row
            execute immediate 'insert into ' || totable
                || '(key, value) values (:key, :value)'
                using l_desc_tab(i).col_name, l_value;
        end loop;
    end loop;
end;
/

我假设您知道 ToTable 中的列名，但仍然使用动态插入语句，因为该表名未知.(这看起来很奇怪，但是...)

I've assumed you know the column names in your ToTable but still used a dynamic insert statement since that table name is unknown. (Which seems strange, but...)

创建和填充示例表，然后使用它们的名称调用过程:

Creating and populating sample tables, and then calling the procedure with their names:

create table source_table (col_name varchar2(30), lib_name varchar2(30),
  partname varchar2(30), primitive number, part_row number,
  col1 varchar2(10), col2 number, col3 date);
create table target_table (key varchar2(30), value varchar2(30));

insert into source_table (col_name, lib_name, partname, primitive, part_row,
  col1, col2, col3)
values ('A', 'B', 'C', 0, 1, 'Test', 42, sysdate);

exec migrate_primitives_props('source_table', 'target_table');

最终目标表包含:

select * from target_table;

KEY                            VALUE                        
------------------------------ ------------------------------
COL1                           Test                          
COL2                           42                            
COL3                           2015-05-22 15:29:31           

这是基本的，因为它没有清理输入(查找 dbms_assert 包)，并且不对不同的数据类型进行任何特殊处理.在我的示例中，我的源表有一个日期列；目标表根据调用会话的 NLS_DATE_FORMAT 设置获取该日期值的字符串表示形式，这并不理想.有一种简单但稍微有点麻烦的方法来获得一致的日期格式，还有一种更好但更复杂的方法；但您可能没有日期值，所以这可能已经足够了.

It's basic because it isn't sanitising the inputs (look up the dbms_assert package), and isn't doing any special handling for different data types. In my example my source table had a date column; the target table gets a string representation of that date value based on the calling session's NLS_DATE_FORMAT setting, which isn't ideal. There's a simple but slightly hacky way to get a consistent date format, and a better but more complicated way; but you may not have date values so this might be good enough as it is.

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