mysql实现oracle存储过程默认参数

function number_stats; CREATE FUNCTION number_stats(in_numbers JSON) RETURNS INTEGER NOT DETERMINISTIC CONTAINS SQL COMMENT ‘Accept an array of integers and their median‘ BEGIN DECLARE v_count INT UNSIGNED DEFAULT JSON_LENGTH(in_numbers); RETURN JSON_EXTRACT( in_numbers, CONCAT(‘$[‘, FLOOR(v_count / 2), ‘]‘) ); END;

mariadb> select number_stats(‘[1,2,3,4]‘);

+---------------------------+
| number_stats(‘[1,2,3,4]‘) |
+---------------------------+
|                         3 |
+---------------------------+
1 row in set

mariadb> select JSON_VALUE(‘{ "x": [0,1], "y": "[0,1]", "z": "Monty" }‘,‘$.z‘);
+----------------------------------------------------------------+
| JSON_VALUE(‘{ "x": [0,1], "y": "[0,1]", "z": "Monty" }‘,‘$.z‘) |
+----------------------------------------------------------------+
| Monty                                                          |
+----------------------------------------------------------------+
1 row in set

mariadb> select JSON_VALUE(‘{ "x": [0,1], "y": "[0,1]", "z": "Monty" }‘,‘$.x
‘);
+----------------------------------------------------------------+
| JSON_VALUE(‘{ "x": [0,1], "y": "[0,1]", "z": "Monty" }‘,‘$.x‘) |
+----------------------------------------------------------------+
| NULL                                                           |
+----------------------------------------------------------------+
1 row in set

mariadb> select JSON_VALUE(‘{ "x": [0,1], "y": "[0,1]", "z": "Monty" }‘,‘$.y
‘);
+----------------------------------------------------------------+
| JSON_VALUE(‘{ "x": [0,1], "y": "[0,1]", "z": "Monty" }‘,‘$.y‘) |
+----------------------------------------------------------------+
| [0,1]                                                          |
+----------------------------------------------------------------+
1 row in set

https://federico-razzoli.com/variable-number-of-parameters-and-optional-parameters-in-mysql-mariadb-procedures

https://mariadb.com/kb/en/library/json_extract/

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