IF(expr1,expr2,expr3)

如果 expr1 是TRUE (expr1 <> 0 and expr1 <> NULL)，则 IF()的返回值为expr2; 否则返回值则为 expr3。IF() 的返回值为数字值或字符串值

SET @sql = NULL;

SELECT

  GROUP_CONCAT(DISTINCT

    CONCAT(

      'MAX(IF(c.label = ''',

      c.label,

      ''', c.value, 0)) AS ''',

      c.label, ''''

    )

  ) INTO @sql

FROM table_name c;

SET @sql = CONCAT('Select phone, ', @sql,

                        ' From table_name  c');

PREPARE stmt FROM @sql;

EXECUTE stmt;

DEALLOCATE PREPARE stmt;