MySQL Store Procedure with Parameter that is a list

MySQL Store Procedure with Parameter that is a list

In MySQL, stored procedures do not directly support parameters that are lists or arrays. However, you can achieve similar functionality by passing a delimited string of values and then parsing this string within the stored procedure. Here's how you can approach it:

Example Approach using Delimited String

Let's say you want to pass a list of IDs (integer values) as a comma-separated string to a stored procedure and use these IDs in a query.

  1. Create the Stored Procedure:
DELIMITER // CREATE PROCEDURE GetEntitiesByIDs(IN idList VARCHAR(255)) BEGIN DECLARE done INT DEFAULT 0; DECLARE id INT; DECLARE cur CURSOR FOR SELECT CAST(trim(substring_index(substring_index(idList, ',', n), ',', -1)) AS UNSIGNED) AS id; DECLARE CONTINUE HANDLER FOR NOT FOUND SET done = 1; SET n = 1; OPEN cur; read_loop: LOOP FETCH cur INTO id; IF done THEN LEAVE read_loop; END IF; -- Use the fetched id in your query, for example: SELECT * FROM entities WHERE entity_id = id; SET n = n + 1; END LOOP; CLOSE cur; END // DELIMITER ;

Explanation:

  • GetEntitiesByIDs Procedure:

    • Accepts a single parameter idList of type VARCHAR(255), which is expected to be a comma-separated list of IDs.
    • Declares variables done, id, and cur for processing the IDs.
    • Uses a cursor (cur) to iterate over the IDs parsed from the idList string.
    • Inside the loop, each id is fetched from the cursor and can be used in subsequent SQL statements (e.g., SELECT, UPDATE, DELETE).

  • Handling Delimited String:

    • CAST(trim(substring_index(substring_index(idList, ',', n), ',', -1)) AS UNSIGNED): This part of the code extracts each ID from the delimited string using MySQL string functions (substring_index) and casts it to UNSIGNED (assuming IDs are integers).

  • Looping through IDs:

    • Uses a LOOP to fetch each ID until no more IDs are found (NOT FOUND).

Calling the Stored Procedure

To call this stored procedure from MySQL:

CALL GetEntitiesByIDs('1,2,3,4,5');

Replace '1,2,3,4,5' with your actual comma-separated list of IDs.

Important Considerations:

  • Security: Ensure that the input idList is properly validated and sanitized to prevent SQL injection vulnerabilities.
  • Performance: Using a delimited string requires parsing and iterating through each value, which may not be as efficient as handling a table-valued parameter in other database systems.

This approach allows you to simulate passing a list or array-like structure to a MySQL stored procedure using a delimited string. Adjust the delimiter and string handling functions (SUBSTRING_INDEX, TRIM, etc.) based on your specific requirements and data format.

Examples

  1. MySQL stored procedure with array parameter

    Description: Creating a MySQL stored procedure that accepts an array or list as a parameter.

    Code/Example:

    DELIMITER // CREATE PROCEDURE sp_process_list(IN list_param VARCHAR(255)) BEGIN DECLARE item VARCHAR(255); DECLARE done INT DEFAULT FALSE; DECLARE cur CURSOR FOR SELECT column_name FROM table_name WHERE id IN (list_param); -- Create temporary table to store results CREATE TEMPORARY TABLE temp_results ( result_column VARCHAR(255) ); -- Open cursor and fetch data OPEN cur; read_loop: LOOP FETCH cur INTO item; IF done THEN LEAVE read_loop; END IF; -- Process each item and insert into temporary table INSERT INTO temp_results (result_column) VALUES (item); END LOOP; -- Close cursor CLOSE cur; -- Select results from temporary table SELECT * FROM temp_results; -- Drop temporary table DROP TEMPORARY TABLE IF EXISTS temp_results; END // DELIMITER ;

    Explanation: This stored procedure sp_process_list accepts a comma-separated list of IDs (list_param) as input. It uses a cursor to fetch data based on these IDs from a table (table_name) and stores the results in a temporary table (temp_results), which is then queried and dropped at the end.

  2. MySQL stored procedure with parameter array

    Description: Handling an array parameter in a MySQL stored procedure to perform operations based on multiple values.

    Code/Example:

    DELIMITER // CREATE PROCEDURE sp_update_multiple(IN list_param VARCHAR(255)) BEGIN DECLARE id_list VARCHAR(255); SET id_list = list_param; -- Use FIND_IN_SET to process each ID in the list UPDATE table_name SET status = 'Updated' WHERE FIND_IN_SET(id, id_list) > 0; END // DELIMITER ;

    Explanation: In this example, sp_update_multiple accepts a comma-separated list of IDs (list_param). It uses FIND_IN_SET to locate each ID within the list and performs an update operation based on those IDs in the table_name table.

  3. MySQL stored procedure with parameter list

    Description: Implementing a MySQL stored procedure with a parameter that is a list of values.

    Code/Example:

    DELIMITER // CREATE PROCEDURE sp_process_multiple(IN list_param VARCHAR(255)) BEGIN DECLARE id INT; DECLARE done INT DEFAULT FALSE; DECLARE cur CURSOR FOR SELECT id FROM table_name WHERE FIND_IN_SET(id, list_param); -- Open cursor and fetch data OPEN cur; read_loop: LOOP FETCH cur INTO id; IF done THEN LEAVE read_loop; END IF; -- Process each ID as needed -- Example: Perform operations on id UPDATE table_name SET processed = true WHERE id = id; END LOOP; -- Close cursor CLOSE cur; END // DELIMITER ;

    Explanation: Here, sp_process_multiple uses FIND_IN_SET to locate IDs within the comma-separated list_param and processes each ID accordingly (e.g., updating a flag in the table_name table).

  4. MySQL stored procedure with dynamic list parameter

    Description: Creating a MySQL stored procedure with a dynamically sized list parameter.

    Code/Example:

    DELIMITER // CREATE PROCEDURE sp_process_dynamic_list(IN list_param TEXT) BEGIN DECLARE pos INT DEFAULT 1; DECLARE id INT; DECLARE delim VARCHAR(255) DEFAULT ','; -- Iterate through the list and process each item WHILE pos <= LENGTH(list_param) DO SET id = SUBSTRING(list_param, pos, LOCATE(delim, list_param, pos) - pos); -- Process id as needed UPDATE table_name SET processed = true WHERE id = id; SET pos = LOCATE(delim, list_param, pos) + 1; IF pos = 1 THEN SET pos = LENGTH(list_param) + 1; END IF; END WHILE; END // DELIMITER ;

    Explanation: sp_process_dynamic_list splits list_param into individual IDs using a delimiter (delim) and iterates through them to perform operations (e.g., updating processed status in table_name).

  5. MySQL stored procedure with JSON array parameter

    Description: Using JSON arrays as parameters in MySQL stored procedures for handling lists.

    Code/Example:

    DELIMITER // CREATE PROCEDURE sp_process_json_array(IN json_param JSON) BEGIN DECLARE id INT; DECLARE done INT DEFAULT FALSE; DECLARE cur CURSOR FOR SELECT id FROM table_name WHERE id IN (SELECT * FROM JSON_TABLE(json_param, '$[*]' COLUMNS(id INT PATH '$'))); -- Open cursor and fetch data OPEN cur; read_loop: LOOP FETCH cur INTO id; IF done THEN LEAVE read_loop; END IF; -- Process each ID as needed -- Example: Update table based on id UPDATE table_name SET processed = true WHERE id = id; END LOOP; -- Close cursor CLOSE cur; END // DELIMITER ;

    Explanation: In sp_process_json_array, json_param is parsed using JSON_TABLE to extract IDs, which are then processed (e.g., updating processed status in table_name).

  6. MySQL stored procedure with comma separated parameter

    Description: Handling a comma-separated parameter list in a MySQL stored procedure.

    Code/Example:

    DELIMITER // CREATE PROCEDURE sp_process_comma_separated(IN list_param VARCHAR(255)) BEGIN DECLARE id VARCHAR(255); DECLARE done INT DEFAULT FALSE; DECLARE cur CURSOR FOR SELECT column_name FROM table_name WHERE FIND_IN_SET(column_name, list_param); -- Open cursor and fetch data OPEN cur; read_loop: LOOP FETCH cur INTO id; IF done THEN LEAVE read_loop; END IF; -- Process each item as needed -- Example: Log or update based on id INSERT INTO log_table (log_message) VALUES ('Processed ID: ' + id); END LOOP; -- Close cursor CLOSE cur; END // DELIMITER ;

    Explanation: This example demonstrates using FIND_IN_SET to locate and process items specified in the comma-separated list_param within table_name, such as inserting log messages into log_table.

  7. MySQL stored procedure with table-valued parameter

    Description: Using a table-valued parameter (e.g., temporary table) in a MySQL stored procedure.

    Code/Example:

    DELIMITER // CREATE PROCEDURE sp_process_table_parameter(IN tbl_param TABLE) BEGIN DECLARE done INT DEFAULT FALSE; DECLARE id INT; DECLARE cur CURSOR FOR SELECT id FROM tbl_param; -- Open cursor and fetch data OPEN cur; read_loop: LOOP FETCH cur INTO id; IF done THEN LEAVE read_loop; END IF; -- Process each ID as needed -- Example: Update status based on id UPDATE table_name SET processed = true WHERE id = id; END LOOP; -- Close cursor CLOSE cur; END // DELIMITER ;

    Explanation: In sp_process_table_parameter, tbl_param represents a table-like parameter (e.g., a temporary table) used to iterate through and process IDs, updating the processed status in table_name.

  8. MySQL stored procedure with array parameter

    Description: Handling an array parameter in MySQL stored procedures for batch operations.

    Code/Example:

    DELIMITER // CREATE PROCEDURE sp_process_array(IN array_param VARCHAR(255)) BEGIN DECLARE id INT; DECLARE done INT DEFAULT FALSE; DECLARE cur CURSOR FOR SELECT id FROM table_name WHERE id IN (SELECT CAST(token AS UNSIGNED) FROM STRING_SPLIT(array_param, ',')); -- Open cursor and fetch data OPEN cur; read_loop: LOOP FETCH cur INTO id; IF done THEN LEAVE read_loop; END IF; -- Process each ID as needed -- Example: Log or update based on id INSERT INTO log_table (log_message) VALUES ('Processed ID: ' + id); END LOOP; -- Close cursor CLOSE cur; END // DELIMITER ;

    Explanation: Here, sp_process_array uses STRING_SPLIT to split array_param into individual IDs, which are then processed (e.g., logging messages into log_table).

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