Question

只是想知道如何创建一个函数来计算mysql内部\ n \ n（连续2个）的数量并将其拆分为不同的别名

类似的东西：

FUNCTION

SELECT COUNT ('paragraphs of a text_field, "\n\n"') AS PRG 
FROM database 
WHERE field_name LIKE '%text%'

WHILE counter < PRG THEN SELECT SUBSTRING_INDEX (text_field, '\n\n', 1)
AS C+counter END WHILE 

END FUNCTION;

输出应该是这样的

对于3段文字：

C1          |C2          |C3
Paragraph 1 |Paragraph 2 |Paragraph 3

对于5段文字：

C1          |C2          |C3          |C4          |C5
Paragraph 1 |Paragraph 2 |Paragraph 3 |Paragraph 4 |Paragraph 5

Answer 1

MariaDB（以及MySQL）不支持拆分和转移 - 如果您在应用程序中进行计算，它肯定会更快。

纯MariaDB / MySQL解决方案将是一个存储过程，如

CREATE PROCEDURE xyz()
BEGIN
  SELECT CHAR_LENGTH(field_name) - CHAR_LENGTH(REPLACE(field_name,"\n\n","")) INTO @a FROM mytbl WHERE fieldname='yourvalue';
  SET @i=1;
  SET @query="SELECT ";
  REPEAT
    SET @query= CONCAT(@query, ' REPLACE(substring_index(field_name, "\n\n", ',@i,'), SUBSTRING_INDEX(field_name,"\n\n", ',@i-1,'), "") AS C',@i,'');
    IF @i < @a THEN 
      SET @query=CONCAT(@query, ",");
    END IF;
    SET @i=@i+1; 
  UNTIL @i > @a END REPEAT; 
  SET @query=CONCAT(@query, " FROM mytbl WHERE field_name='yourvalue'");
  PREPARE my FROM @query;
  EXECUTE my;
END

计算并拆分成mysql

1 个答案: