拼接查询sql中指定列的结果集
拼接查询sql中指定列的结果集
函数适用于:需要将指定查询sql中的某列拼接成以指定字符分隔连接的字符串。
不足:因函数的返回值为varchar2,且通常拼接得到的字符串会用于查询sql(因用在SQL中,不能大于varchar2的4000个字符限制)中,因此限制了返回长度小于等于4000
- CREATE OR REPLACE FUNCTION f_con_colunn_set(p_sql IN VARCHAR2,
- --传入的sql语句
- p_column_index INTEGER DEFAULT 1,
- --需要连接的字段索引位置(从1开始,默认为1)
- p_con_str IN VARCHAR2 DEFAULT ','
- --连接时的分隔符,默认为逗号
- ) RETURN VARCHAR2 IS
- /*适用于需要将sql语句的某列查询结果(大于一条记录)拼接成一个字段返回,
- 限制了返回长度小于等于4000(因用在SQL中,不能大于varchar2的4000个字符限制)
- */
- v_value VARCHAR2(4000);
- v_return VARCHAR2(8000) := '';
- sqlstr_cursor INTEGER;
- v_ignore INTEGER;
- v_name INTEGER;
- v_col_count INTEGER;
- v_column_desc dbms_sql.desc_tab;
- BEGIN
- v_name := dbms_sql.open_cursor;
- dbms_sql.parse(v_name, p_sql, dbms_sql.native);
- dbms_sql.describe_columns(v_name, v_col_count, v_column_desc);
- DBMS_SQL.close_cursor(v_name);
- IF p_column_index > 0 AND p_column_index <= v_col_count THEN
- sqlstr_cursor := DBMS_SQL.open_cursor;
- DBMS_SQL.parse(sqlstr_cursor, p_sql, DBMS_SQL.native);
- DBMS_SQL.define_column(sqlstr_cursor,
- p_column_index,
- v_column_desc(p_column_index).col_name,
- 4000);
- v_ignore := DBMS_SQL.EXECUTE(sqlstr_cursor);
- LOOP
- IF DBMS_SQL.fetch_rows(sqlstr_cursor) > 0 THEN
- DBMS_SQL.COLUMN_VALUE(sqlstr_cursor, p_column_index, v_value);
- IF length(v_return || v_value) > 4000 THEN
- EXIT;
- ELSE
- v_return := v_return || p_con_str || v_value;
- END IF;
- ELSE
- EXIT;
- END IF;
- END LOOP;
- v_return := substr(v_return, length(p_con_str) + 1, 4000);
- DBMS_SQL.close_cursor(sqlstr_cursor);
- END IF;
- RETURN v_return;
- EXCEPTION
- WHEN OTHERS THEN
- IF DBMS_SQL.is_open(v_name) THEN
- DBMS_SQL.close_cursor(v_name);
- END IF;
- IF DBMS_SQL.is_open(sqlstr_cursor) THEN
- DBMS_SQL.close_cursor(sqlstr_cursor);
- END IF;
- RETURN '';
- END f_con_colunn_set;
--测试方法
--1)只传SQL,默认返回col1的以逗号分隔连接值:test1,test2
SELECT f_con_colunn_set('select ''test1'' col1,1 col2 from dual union all select ''test2'' col1,2 col2 from dual')
FROM dual;
--2)传SQL,传col2的索引值(从1开始),返回col2以逗号分隔的连接值: 1,2
SELECT f_con_colunn_set('select ''test1'' col1,1 col2 from dual union all select ''test2'' col1,2 col2 from dual',
2)
FROM dual;
--3)传SQL,传col2的索引值(从1开始),分隔值';',返回col2以分号号分隔的连接值1;2
SELECT f_con_colunn_set('select ''test1'' col1,1 col2 from dual union all select ''test2'' col1,2 col2 from dual',
2,
';')
FROM dual;
--4)传SQL,传索引值(从1开始)3,传入的索引值超过SQL的列索引集合,不存在此列,返回空值
SELECT f_con_colunn_set('select ''test1'' col1,1 col2 from dual union all select ''test2'' col1,2 col2 from dual',
3)
FROM dual;
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