再来一篇水文:-)
主要是想把Steven写的intab贴过来，以方便平时参考参考下。这个intab主要是关于DBMS_SQL的用法，也就是Steven说的关于动态SQL的Method4的典型应用。关于DBMS_SQL, 我在另外一片水文也贴过，see here.
关于动态SQL的4中method, 参考下图...
不废话，直接贴代码...
CREATE OR REPLACE PROCEDURE intab (
table_in IN VARCHAR2
,where_in IN VARCHAR2 DEFAULT NULL
,colname_like_in IN VARCHAR2 := '%'
)
AUTHID CURRENT_USER
/*
"In Table" utility: use DBMS_SQL to implement a Method 4 dynamic SQL challenge.
Author: Steven Feuerstein, steven@stevenfeuerstein.com
Date: July 2005
You have my permission to use the code found in this program for your own use.
Overview:
Show the rows of the table specified by the table name and optional where clause.
This is more of a prototype than a production-quality utility; its main purpose
is to provide a demonstration of the steps you must go through to implement
Method 4 dynamic SQL with DBMS_SQL.
Method 4 means that at the time you are writing your program, you either don't
know the number and types of columns being selected or you don't know the
number of bind variables in the dynamic string.
In this case, since the user can supply the table name, we have no way of knowing
which columns (and how many) will need to be selected. We will get the column
information from ALL_TAB_COLUMNS and then use that to drive the dynamic SQL
processing with DBMS_SQL.
Note: in most cases, you will want to use Native Dynamic SQL for dynamic SQL
requirements. DBMS_SQL is, however, very well suited to implementing Method 4.
Parameters:
table_in - name of the table or view, in the form schema.table or table.
where_in - optional where clause. Do not include the WHERE keyword. If, however,
you start the where clause with ORDER BY or GROUP BY, then that
entire string will be added to the query. Your where clause could
also contain an ORDER BY or GROUP BY after the where clause.
colname_like_in - an optional filter that is applied to the set of columns
to restrict which columns are displayed. A NULL value is
treated as "%" - all columns.
Requirements:
* Oracle91 Database or higher: intab BULK COLLECTs into a collection of records.
Restrictions of functionality in intab:
* Prior to Oracle Database 10g Release 2, The contents of a row, converted to
a string, cannot be longer than 255 characters. In Oracle10g Database Release 2,
up to 32767 characters are supported.
* Datatypes of columns must be string, number or date -- or be of a type that can
implicitly converted to one of these types.
* Does not support table or column names that contain double quotes.
*/
IS
-- Avoid repetitive "maximum size" declarations for VARCHAR2 variables.
SUBTYPE max_varchar2_t IS VARCHAR2 (32767);
-- Minimize size of a string column.
c_min_length CONSTANT PLS_INTEGER := 10;
-- Collection to hold the column information for this table.
TYPE columns_tt IS TABLE OF all_tab_columns%ROWTYPE
INDEX BY PLS_INTEGER;
g_columns columns_tt;
--
-- Open a cursor for use by DBMS_SQL subprograms throughout this procedure.
g_cursor INTEGER := DBMS_SQL.open_cursor;
--
-- Formatting and SELECT elements used throughout the program.
g_header max_varchar2_t;
g_select_list max_varchar2_t;
g_row_line_length INTEGER := 0;
/* Utility functions that determine the "family" of the column datatype.
They do NOT comprehensively cover the datatypes supported by Oracle.
You will need to expand on these programs if you want your version of
intab to support a wider range of datatypes.
*/
FUNCTION is_string (row_in IN INTEGER)
RETURN BOOLEAN
IS
BEGIN
RETURN (g_columns (row_in).data_type IN
('CHAR', 'VARCHAR2', 'VARCHAR')
);
END;
FUNCTION is_number (row_in IN INTEGER)
RETURN BOOLEAN
IS
BEGIN
RETURN (g_columns (row_in).data_type IN
('FLOAT', 'INTEGER', 'NUMBER')
);
END;
FUNCTION is_date (row_in IN INTEGER)
RETURN BOOLEAN
IS
BEGIN
RETURN (g_columns (row_in).data_type IN ('DATE', 'TIMESTAMP'));
END;
PROCEDURE load_column_information
IS
l_dot_location PLS_INTEGER;
l_owner VARCHAR2 (100);
l_table VARCHAR2 (100);
l_index PLS_INTEGER;
--
no_such_table EXCEPTION;
PRAGMA EXCEPTION_INIT (no_such_table, -942);
BEGIN
-- Separate the schema and table names, if both are present.
l_dot_location := INSTR (table_in, '.');
IF l_dot_location > 0
THEN
l_owner := SUBSTR (table_in, 1, l_dot_location - 1);
l_table := SUBSTR (table_in, l_dot_location + 1);
ELSE
l_owner := USER;
l_table := table_in;
END IF;
-- Retrieve all the column information into a collection of records.
SELECT *
BULK COLLECT INTO g_columns
FROM all_tab_columns
WHERE owner = l_owner
AND table_name = l_table
AND column_name LIKE NVL (colname_like_in, '%');
l_index := g_columns.FIRST;
IF l_index IS NULL
THEN
RAISE no_such_table;
ELSE
/* Add each column to the select list, calculate the length needed
to display each column, and also come up with the total line length.
Again, please note that the datatype support here is quite limited.
*/
WHILE (l_index IS NOT NULL)
LOOP
IF g_select_list IS NULL
THEN
g_select_list := g_columns (l_index).column_name;
ELSE
g_select_list :=
g_select_list || ', ' || g_columns (l_index).column_name;
END IF;
IF is_string (l_index)
THEN
g_columns (l_index).data_length :=
GREATEST (LEAST (g_columns (l_index).data_length
,c_min_length
)
,LENGTH (g_columns (l_index).column_name)
);
ELSIF is_date (l_index)
THEN
g_columns (l_index).data_length :=
GREATEST (c_min_length
,LENGTH (g_columns (l_index).column_name)
);
ELSIF is_number (l_index)
THEN
g_columns (l_index).data_length :=
GREATEST (NVL (g_columns (l_index).data_precision, 38)
,LENGTH (g_columns (l_index).column_name)
);
END IF;
g_row_line_length :=
g_row_line_length + g_columns (l_index).data_length + 1;
--
-- Construct column header line incrementally.
g_header :=
g_header
|| ' '
|| RPAD (g_columns (l_index).column_name
,g_columns (l_index).data_length
);
l_index := g_columns.NEXT (l_index);
END LOOP;
END IF;
END load_column_information;
PROCEDURE construct_and_parse_query
IS
l_where_clause max_varchar2_t := LTRIM (UPPER (where_in));
l_query max_varchar2_t;
BEGIN
-- Construct a where clause if a value was specified.
IF l_where_clause IS NOT NULL
THEN
--
IF ( l_where_clause NOT LIKE 'GROUP BY%'
AND l_where_clause NOT LIKE 'ORDER BY%'
)
THEN
l_where_clause := 'WHERE ' || LTRIM (l_where_clause, 'WHERE');
END IF;
END IF;
-- Assign the dynamic string to a local variable so that it can be
-- easily used to report an error.
l_query :=
'SELECT '
|| g_select_list
|| ' FROM '
|| table_in
|| ' '
|| l_where_clause;
/*
DBMS_SQL.PARSE
Parse the SELECT statement; it is a very generic one, combining
the list of columns drawn from ALL_TAB_COLUMNS, the table name
provided by the user, and the optional where clause.
Use the DBMS_SQL.NATIVE constant to indicate that DBMS_SQL should
use the native SQL parser for the current version of Oracle
to parse the statement.
*/
DBMS_SQL.parse (g_cursor, l_query, DBMS_SQL.native);
EXCEPTION
WHEN OTHERS
THEN
DBMS_OUTPUT.put_line ('Error parsing query:');
DBMS_OUTPUT.put_line (l_query);
RAISE;
END construct_and_parse_query;
PROCEDURE define_columns_and_execute
IS
l_index PLS_INTEGER;
l_feedback PLS_INTEGER;
BEGIN
/*
DBMS_SQL.DEFINE_COLUMN
Before executing the query, I need to tell DBMS_SQL the datatype
of each the columns being selected in the query. I simply pass
a literal of the appropriate type to an overloading of
DBMS_SQL.DEFINE_COLUMN. With string types, I need to also specify
the maximum length of the value.
*/
l_index := g_columns.FIRST;
WHILE (l_index IS NOT NULL)
LOOP
IF is_string (l_index)
THEN
DBMS_SQL.define_column (g_cursor
,l_index
,'a'
,g_columns (l_index).data_length
);
ELSIF is_number (l_index)
THEN
DBMS_SQL.define_column (g_cursor, l_index, 1);
ELSIF is_date (l_index)
THEN
DBMS_SQL.define_column (g_cursor, l_index, SYSDATE);
END IF;
l_index := g_columns.NEXT (l_index);
END LOOP;
l_feedback := DBMS_SQL.EXECUTE (g_cursor);
END define_columns_and_execute;
PROCEDURE build_and_display_output
IS
-- Used to hold the retrieved column values.
l_string_value VARCHAR2 (2000);
l_number_value NUMBER;
l_date_value DATE;
--
l_feedback INTEGER;
l_index PLS_INTEGER;
l_one_row_string max_varchar2_t;
-- Formatting for the output of the header information
PROCEDURE display_header
IS
l_border max_varchar2_t := RPAD ('-', g_row_line_length, '-');
FUNCTION centered_string (
string_in IN VARCHAR2
,length_in IN INTEGER
)
RETURN VARCHAR2
IS
len_string INTEGER := LENGTH (string_in);
BEGIN
IF len_string IS NULL OR length_in <= 0
THEN
RETURN NULL;
ELSE
RETURN RPAD (' ', (length_in - len_string) / 2 - 1)
|| LTRIM (RTRIM (string_in));
END IF;
END centered_string;
BEGIN
DBMS_OUTPUT.put_line (l_border);
DBMS_OUTPUT.put_line (centered_string ('Contents of ' || table_in
,g_row_line_length
)
);
DBMS_OUTPUT.put_line (l_border);
DBMS_OUTPUT.put_line (g_header);
DBMS_OUTPUT.put_line (l_border);
END display_header;
BEGIN
display_header;
-- Fetch one row at a time, until the last has been fetched.
LOOP
/*
DBMS_SQL.FETCH_ROWS
Fetch a row, and return the numbers of rows fetched.
When 0, we are done.
*/
l_feedback := DBMS_SQL.fetch_rows (g_cursor);
EXIT WHEN l_feedback = 0;
--
l_one_row_string := NULL;
l_index := g_columns.FIRST;
WHILE (l_index IS NOT NULL)
LOOP
/*
DBMS_SQL.COLUMN_VALUE
Retrieve each column value in the current row,
deposit it into a variable of the appropriate type,
then convert to a string and concatenate to the
full line variable.
*/
IF is_string (l_index)
THEN
DBMS_SQL.column_value (g_cursor, l_index, l_string_value);
ELSIF is_number (l_index)
THEN
DBMS_SQL.column_value (g_cursor, l_index, l_number_value);
l_string_value := TO_CHAR (l_number_value);
ELSIF is_date (l_index)
THEN
DBMS_SQL.column_value (g_cursor, l_index, l_date_value);
l_string_value := TO_CHAR (l_date_value);
END IF;
l_one_row_string :=
l_one_row_string
|| ' '
|| RPAD (NVL (l_string_value, ' ')
,g_columns (l_index).data_length
);
l_index := g_columns.NEXT (l_index);
END LOOP;
DBMS_OUTPUT.put_line (l_one_row_string);
END LOOP;
END build_and_display_output;
PROCEDURE cleanup
IS
BEGIN
/*
DBMS_SQL.CLOSE_CURSOR
Make sure to close the cursor on both successful completion
and when an error is raised.
*/
DBMS_SQL.close_cursor (g_cursor);
END cleanup;
BEGIN
/*
I keep the executable section small and very readable by creating
a series of local subprograms to perform the tasks required.
*/
load_column_information;
construct_and_parse_query;
define_columns_and_execute;
build_and_display_output;
cleanup;
EXCEPTION
WHEN OTHERS
THEN
cleanup;
RAISE;
END intab;
/
--EOF--
