mysql在sql语法中计算单词[重复]

Question

让我们来一个简单的查询：

SELECT myfield
FROM   mytable
WHERE  criteria

例如，上面的查询给了我们 10 行的结果。字段myField 是一个文本字段。

我的问题是：是否可以更改上述查询并获得myField 字段的总字数？

已编辑：总字数是指查询中所有选定字段的总字数，在所有行中

示例

+------------------------------+-------+
| sentence                     | Words |
+------------------------------+-------+
| Hello World                  |     2 |
| Hello World                  |     2 |
| Mary had a little lamb       |     5 |
| Her fleece was white as snow |     6 |
| Everywhere that mary went    |     4 |
| Umm, sheep followed her      |     4 |
+------------------------------+-------+

Answer 1

在您的查询中使用来自@otis 的this question 的出色功能：

mysql> select * from test;
+----+------------------------------+
| id | sentence                     |
+----+------------------------------+
|  0 | Hello World                  |
|  1 | Hello World                  |
|  2 | Mary had a little lamb       |
|  3 | Her fleece was white as snow |
|  4 | Everywhere that mary went    |
|  5 | Umm, sheep followed her      |
+----+------------------------------+
6 rows in set (0.00 sec)

mysql> SELECT sentence, wordcount(sentence) as "Words" from test;
+------------------------------+-------+
| sentence                     | Words |
+------------------------------+-------+
| Hello World                  |     2 |
| Hello World                  |     2 |
| Mary had a little lamb       |     5 |
| Her fleece was white as snow |     6 |
| Everywhere that mary went    |     4 |
| Umm, sheep followed her      |     4 |
+------------------------------+-------+
6 rows in set (0.02 sec)

要使函数工作，你需要在 MySQL 中执行函数的声明。就像执行任何其他查询一样：

mysql> DELIMITER $$
mysql> CREATE FUNCTION wordcount(str TEXT)
            RETURNS INT
            DETERMINISTIC
            SQL SECURITY INVOKER
            NO SQL
       BEGIN
         DECLARE wordCnt, idx, maxIdx INT DEFAULT 0;
         DECLARE currChar, prevChar BOOL DEFAULT 0;
         SET maxIdx=char_length(str);
         WHILE idx < maxIdx DO
             SET currChar=SUBSTRING(str, idx, 1) RLIKE '[[:alnum:]]';
             IF NOT prevChar AND currChar THEN
                 SET wordCnt=wordCnt+1;
             END IF;
             SET prevChar=currChar;
             SET idx=idx+1;
         END WHILE;
         RETURN wordCnt;
       END
     $$
Query OK, 0 rows affected (0.10 sec)

mysql> DELIMITER ;