MySQL Cursor 静默删除尾随空格

Question

我正在编写一个存储过程，它从给定列中获取一些数据并对其进行处理，问题是其中一些数据包含尾随空格，并且当数据由于某种原因被读入存储过程中的临时表时那些尾随空格被删除（我需要保留它们）。

我已将罪魁祸首缩小到光标的声明..

DECLARE curs CURSOR FOR SELECT element, LENGTH(element) FROM tmpTable;

如果我打印出每个循环中光标包含的内容，则元素类似于“1234”，但长度为 8.. 这是我想要的，因为原始数据是“1234”。

关于如何使光标读取所有内容而不是默默地修剪尾随空格的任何想法？

Answer 1

我无法重现该问题。

注意LENGTH() 和CHAR_LENGTH() 之间的区别。

mysql> SELECT VERSION();
+-----------+
| VERSION() |
+-----------+
| 5.7.13    |
+-----------+
1 row in set (0.00 sec)

mysql> DROP TABLE IF EXISTS `tmpTable`;
Query OK, 0 rows affected (0.00 sec)

mysql> DROP PROCEDURE IF EXISTS `demo_sp`;
Query OK, 0 rows affected (0.00 sec)

mysql> CREATE TABLE IF NOT EXISTS `tmpTable` (
    ->   `element_utf8` VARCHAR(50),
    ->   `element_latin1` VARCHAR(50) CHARACTER SET latin1 COLLATE latin1_spanish_ci
    -> ) CHARACTER SET=utf8;
Query OK, 0 rows affected (0.00 sec)

mysql> INSERT INTO `tmpTable`
    ->   (`element_utf8`, `element_latin1`)
    -> VALUES
    ->   (CONCAT('1234', SPACE(5)), CONCAT('1234', SPACE(5))),
    ->   ('áéíóú', 'áéíóú');
Query OK, 2 rows affected (0.00 sec)
Records: 2  Duplicates: 0  Warnings: 0

mysql> SELECT
    ->   `element_utf8`,
    ->   `element_latin1`,
    ->   LENGTH(`element_utf8`),
    ->   CHAR_LENGTH(`element_utf8`),
    ->   LENGTH(`element_latin1`),
    ->   CHAR_LENGTH(`element_latin1`)
    -> FROM
    ->   `tmpTable`\G
*************************** 1. row ***************************
                 element_utf8: 1234     
               element_latin1: 1234     
       LENGTH(`element_utf8`): 9
  CHAR_LENGTH(`element_utf8`): 9
     LENGTH(`element_latin1`): 9
CHAR_LENGTH(`element_latin1`): 9
*************************** 2. row ***************************
                 element_utf8: áéíóú
               element_latin1: áéíóú
       LENGTH(`element_utf8`): 10
  CHAR_LENGTH(`element_utf8`): 5
     LENGTH(`element_latin1`): 5
CHAR_LENGTH(`element_latin1`): 5
2 rows in set (0.00 sec)

mysql> DELIMITER //

mysql> CREATE PROCEDURE `demo_sp`()
    -> BEGIN
    ->   DECLARE `_not_found` BOOL DEFAULT FALSE;
    ->   DECLARE `_length_utf8`,
    ->           `_char_length_utf8`,
    ->           `_length_latin1`,
    ->           `_char_length_latin1` INT UNSIGNED;
    -> 
    ->   DECLARE `demo_cursor` CURSOR FOR
    ->     SELECT
    ->       LENGTH(`element_utf8`),
    ->       CHAR_LENGTH(`element_utf8`),
    ->       LENGTH(`element_latin1`),
    ->       CHAR_LENGTH(`element_latin1`)
    ->     FROM
    ->       `tmpTable`;
    ->   DECLARE CONTINUE HANDLER FOR NOT FOUND SET `_not_found` := TRUE;
    -> 
    ->   OPEN `demo_cursor`;
    -> 
    ->   `read_loop`: LOOP
    ->     FETCH `demo_cursor` INTO `_length_utf8`,
    ->                              `_char_length_utf8`,
    ->                              `_length_latin1`,
    ->                              `_char_length_latin1`;
    -> 
    ->     IF (`_not_found`) THEN
    ->       CLOSE `demo_cursor`;
    ->       LEAVE `read_loop`;
    ->     END IF;
    -> 
    ->     SELECT `_length_utf8`,
    ->            `_char_length_utf8`,
    ->            `_length_latin1`,
    ->            `_char_length_latin1`;
    ->   END LOOP;
    -> END//
Query OK, 0 rows affected (0.00 sec)

mysql> DELIMITER ;

mysql> CALL `demo_sp`;
+----------------+---------------------+------------------+-----------------------+
| `_length_utf8` | `_char_length_utf8` | `_length_latin1` | `_char_length_latin1` |
+----------------+---------------------+------------------+-----------------------+
|              9 |                   9 |                9 |                     9 |
+----------------+---------------------+------------------+-----------------------+
1 row in set (0.01 sec)

+----------------+---------------------+------------------+-----------------------+
| `_length_utf8` | `_char_length_utf8` | `_length_latin1` | `_char_length_latin1` |
+----------------+---------------------+------------------+-----------------------+
|             10 |                   5 |                5 |                     5 |
+----------------+---------------------+------------------+-----------------------+
1 row in set (0.01 sec)

Query OK, 0 rows affected (0.01 sec)