I want to select from table where the table name is a local variable and the column name is another local variable but i get the following error :
The specified table ll_tb_name
is not in the database
CREATE PROCEDURE rmg_request_file ( al_task_code integer)
RETURNING integer as byte;
DEFINE ll_task_code integer;
DEFINE ll_pdf_column varchar(50);
DEFINE ll_tb_name varchar(60);
DEFINE ll_request_file REFERENCES BYTE;
SELECT pdf_column,table_name INTO ll_pdf_column ,ll_tb_name FROM rnmtask WHERE task_code = al_task_code;
FOREACH
SELECT ll_pdf_column into ll_request_file FROM ll_tb_name
return ll_request_file with resume ;
end foreach;
end procedure
Assuming you have a recent enough version of Informix (11.70), you should be able to use Dynamic SQL in SPL like this:
BEGIN;
CREATE TABLE rnmtask
(
pdf_column VARCHAR(32) NOT NULL,
table_name VARCHAR(32) NOT NULL,
task_code INTEGER NOT NULL PRIMARY KEY
);
INSERT INTO rnmtask VALUES("symbol", "elements", 1);
INSERT INTO rnmtask VALUES("name", "elements", 2);
INSERT INTO rnmtask VALUES("atomic_number", "elements", 3);
CREATE PROCEDURE rmg_request_file(al_task_code INTEGER)
RETURNING VARCHAR(255) AS colval;
DEFINE ll_pdf_column VARCHAR(50);
DEFINE ll_tb_name VARCHAR(60);
DEFINE stmt VARCHAR(255);
DEFINE result VARCHAR(255);
SELECT pdf_column, table_name
INTO ll_pdf_column, ll_tb_name
FROM rnmtask
WHERE task_code = al_task_code;
LET stmt = "SELECT " || ll_pdf_column || " FROM " || ll_tb_name;
PREPARE p FROM stmt;
DECLARE C CURSOR FOR p;
OPEN C;
WHILE sqlcode = 0
FETCH C INTO result;
IF sqlcode != 0 THEN
EXIT WHILE;
END IF;
RETURN result WITH RESUME;
END WHILE;
CLOSE C;
FREE C;
FREE p;
END PROCEDURE;
EXECUTE PROCEDURE rmg_request_file(1);
EXECUTE PROCEDURE rmg_request_file(2);
EXECUTE PROCEDURE rmg_request_file(3);
ROLLBACK;
This assumes you have a convenient Table of Elements in your database:
CREATE TABLE elements
(
atomic_number INTEGER NOT NULL PRIMARY KEY CONSTRAINT c1_elements
CHECK (atomic_number > 0 AND atomic_number < 120),
symbol CHAR(3) NOT NULL UNIQUE CONSTRAINT c2_elements,
name CHAR(20) NOT NULL UNIQUE CONSTRAINT c3_elements,
atomic_weight DECIMAL(8, 4) NOT NULL,
period SMALLINT NOT NULL
CHECK (period BETWEEN 1 AND 7),
group CHAR(2) NOT NULL
-- 'L' for Lanthanoids, 'A' for Actinoids
CHECK (group IN ('1', '2', 'L', 'A', '3', '4', '5', '6',
'7', '8', '9', '10', '11', '12', '13',
'14', '15', '16', '17', '18')),
stable CHAR(1) DEFAULT 'Y' NOT NULL
CHECK (stable IN ('Y', 'N'))
);
INSERT INTO elements VALUES( 1, 'H', 'Hydrogen', 1.0079, 1, '1', 'Y');
INSERT INTO elements VALUES( 2, 'He', 'Helium', 4.0026, 1, '18', 'Y');
INSERT INTO elements VALUES( 3, 'Li', 'Lithium', 6.9410, 2, '1', 'Y');
INSERT INTO elements VALUES( 4, 'Be', 'Beryllium', 9.0122, 2, '2', 'Y');
INSERT INTO elements VALUES( 5, 'B', 'Boron', 10.8110, 2, '13', 'Y');
INSERT INTO elements VALUES( 6, 'C', 'Carbon', 12.0110, 2, '14', 'Y');
INSERT INTO elements VALUES( 7, 'N', 'Nitrogen', 14.0070, 2, '15', 'Y');
INSERT INTO elements VALUES( 8, 'O', 'Oxygen', 15.9990, 2, '16', 'Y');
INSERT INTO elements VALUES( 9, 'F', 'Fluorine', 18.9980, 2, '17', 'Y');
INSERT INTO elements VALUES( 10, 'Ne', 'Neon', 20.1800, 2, '18', 'Y');
INSERT INTO elements VALUES( 11, 'Na', 'Sodium', 22.9900, 3, '1', 'Y');
INSERT INTO elements VALUES( 12, 'Mg', 'Magnesium', 24.3050, 3, '2', 'Y');
INSERT INTO elements VALUES( 13, 'Al', 'Aluminium', 26.9820, 3, '13', 'Y');
INSERT INTO elements VALUES( 14, 'Si', 'Silicon', 28.0860, 3, '14', 'Y');
INSERT INTO elements VALUES( 15, 'P', 'Phosphorus', 30.9740, 3, '15', 'Y');
INSERT INTO elements VALUES( 16, 'S', 'Sulphur', 32.0650, 3, '16', 'Y');
INSERT INTO elements VALUES( 17, 'Cl', 'Chlorine', 35.4530, 3, '17', 'Y');
INSERT INTO elements VALUES( 18, 'Ar', 'Argon', 39.9480, 3, '18', 'Y');
我认为即使在SELECT INTO
,也应在所有出现的ll_tb_name
和ll_pdf_column
加上@符号ll_tb_name
前缀
Use NDS (native dynamic SQL):
EXECUTE IMMEDIATE "SELECT ll_pdf_column into ll_request_file FROM :@ll_tb_name"
USING @ll_tb_name;
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