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Call a lua procedure with:
SELECT client,MONTH(date),SUM(Value) FROM table PROCEDURE lua ( "myscript.lua", parameter_1, parameter_2, .. )

Example procedure:
SELECT client,MONTH(act_date),SUM(Value) FROM table PROCEDURE lua ( "/usr/src/mysql/sql/months.lua", "TEST" ); The procedure take data from the query: "SELECT client,MONTH(date),SUM(Value)"
and change the result set in:

| client | January | ...................... | December |
| cli001 |   100   | ...................... |   200    |
| cli002 |   110   | ...................... |   212    |

Variables defined by MySQL
The MySQL part defines this variables available to the LUA procedure PARAMETERS - parameters passed from the SQL statement FIELDS - field definition for the result set ROWS - contents of the result set

Global variables defined inside MySQL, always defined PARAMETERS[n] = n-th parameter

Defined before the call to "change_columns" and used after "change_columns" to define the new result set.
FIELDS.num = number of fields in the result set FIELDS[n].name = name of the n-th field of the result set FIELDS[n].type = type of the n-th field of the result set. Can be:

                 "STRING","INTEGER" or "REAL".
                 Other setting are interpreted such as "STRING".

FIELDS[n].length =for "STRING" type fields is the max length of the n-th field; for "REAL" type fields is the number of the digit in the decimal part.

Defined before the call to "end_of_records" and used after "end_of_records" to define the result set new contents. ROWS.num = number of rows in the result set ROWS[x][y] = value of the field at position x,y

LUA functions calling order
When MySQL calls a LUA script it calls the following functions in this order:

init ()
When the procedure is initialized
FIELDS and ROWS structures are not defined.

change_columns ()
FIELDS structure is defined with the data from the SELECT statement. The function can change FIELDS to define the result set structure. ROWS structure is undefined.

end_of_records ()
ROWS structure is defined and contains the data from the SELECT statement. The function can change ROWS to define the data of the new result set.