MySQL实现字符串分割split并获取长度
2024-05-11 20:14:00
文章目录
- 问题描述
- 解决方案
- 行转列
- 统计长度
- TODO：创建函数
- 遇到的坑
- 参考文献
问题描述
数据库中有些数据以半角逗号 , 为分隔符，需要获取分割后的值或长度
-- 创建表
CREATE TABLE `person` (`id` int(11) NOT NULL AUTO_INCREMENT COMMENT '用户ID',`name` varchar(255) NOT NULL COMMENT '用户名',`hobby` text NOT NULL COMMENT '爱好，多个用英文逗号分隔',PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=4 DEFAULT CHARSET=utf8;-- 插入数据
INSERT INTO `person` VALUES (1, '刘一', '拳击,击剑');
INSERT INTO `person` VALUES (2, '陈二', '篮球,足球,排球');
INSERT INTO `person` VALUES (3, '张三', '跑步,羽毛球,乒乓球');
INSERT INTO `person` VALUES (4, '李四', '羽毛球');
INSERT INTO `person` VALUES (5, '王五', '1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,31,32,33,34,35,36,37,38,39,40,41,42,43,44,45,46,47,48,49,50,51,52,53,54,55,56,57,58,59,60,61,62,63,64,65,66,67,68,69,70,71,72,73,74,75,76,77,78,79,80,81,82,83,84,85,86,87,88,89,90,91,92,93,94,95,96,97,98,99,100,101,102,103,104,105,106,107,108,109,110,111,112,113,114,115,116,117,118,119,120,121,122,123,124,125,126,127,128,129,130,131,132,133,134,135,136,137,138,139,140,141,142,143,144,145,146,147,148,149,150,151,152,153,154,155,156,157,158,159,160,161,162,163,164,165,166,167,168,169,170,171,172,173,174,175,176,177,178,179,180,181,182,183,184,185,186,187,188,189,190,191,192,193,194,195,196,197,198,199,200,201,202,203,204,205,206,207,208,209,210,211,212,213,214,215,216,217,218,219,220,221,222,223,224,225,226,227,228,229,230,231,232,233,234,235,236,237,238,239,240,241,242,243,244,245,246,247,248,249,250,251,252,253,254,255,256,257,258,259,260,261,262,263,264,265,266,267,268,269,270,271,272,273,274,275,276,277,278,279,280,281,282,283,284,285,286,287,288,289,290,291,292,293,294,295,296,297,298,299,300,301,302,303,304,305,306,307,308,309,310,311,312,313,314,315,316,317,318,319,320,321,322,323,324,325,326,327,328,329,330,331,332,333,334,335,336,337,338,339,340,341,342,343,344,345,346,347,348,349,350,351,352,353,354,355,356,357,358,359,360,361,362,363,364,365,366,367,368,369,370,371,372,373,374,375,376,377,378,379,380,381,382,383,384,385,386,387,388,389,390,391,392,393,394,395,396,397,398,399,400,401,402,403,404,405,406,407,408,409,410,411,412,413,414,415,416,417,418,419,420,421,422,423,424,425,426,427,428,429,430,431,432,433,434,435,436,437,438,439,440,441,442,443,444,445,446,447,448,449,450,451,452,453,454,455,456,457,458,459,460,461,462,463,464,465,466,467,468,469,470,471,472,473,474,475,476,477,478,479,480,481,482,483,484,485,486,487,488,489,490,491,492,493,494,495,496,497,498,499,500,501,502,503,504,505,506,507,508,509,510,511,512,513,514,515,516,517,518,519,520,521,522,523,524,525,526,527,528,529,530,531,532,533,534,535,536,537,538,539,540,541,542,543,544,545,546,547,548,549,550,551,552,553,554,555,556,557,558,559,560,561,562,563,564,565,566,567,568,569,570,571,572,573,574,575,576,577,578,579,580,581,582,583,584,585,586,587,588,589,590,591,592,593,594,595,596,597,598,599,600,601,602,603,604,605,606,607,608,609,610,611,612,613,614,615,616,617,618,619,620,621,622,623,624,625,626,627,628,629,630,631,632,633,634,635,636,637,638,639,640,641,642,643,644,645,646,647,648,649,650,651,652,653,654,655,656,657,658,659,660,661,662,663,664,665,666,667,668,669,670,671,672,673,674,675,676,677,678,679,680,681,682,683,684,685,686,687,688,689,690,691,692,693,694,695,696,697,698,699,700,701,702,703,704,705,706,707,708,709,710,711,712,713,714,715,716,717,718,719,720,721,722,723,724,725,726,727,728,729,730,731,732,733,734,735,736,737,738,739,740,741,742,743,744,745,746,747,748,749,750,751,752,753,754,755,756,757,758,759,760,761,762,763,764,765,766,767,768,769,770,771,772,773,774,775,776,777,778,779,780,781,782,783,784,785,786,787,788,789,790,791,792,793,794,795,796,797,798,799,800,801,802,803,804,805,806,807,808,809,810,811,812,813,814,815,816,817,818,819,820,821,822,823,824,825,826,827,828,829,830,831,832,833,834,835,836,837,838,839,840,841,842,843,844,845,846,847,848,849,850,851,852,853,854,855,856,857,858,859,860,861,862,863,864,865,866,867,868,869,870,871,872,873,874,875,876,877,878,879,880,881,882,883,884,885,886,887,888,889,890,891,892,893,894,895,896,897,898,899,900,901,902,903,904,905,906,907,908,909,910,911,912,913,914,915,916,917,918,919,920,921,922,923,924,925,926,927,928,929,930,931,932,933,934,935,936,937,938,939,940,941,942,943,944,945,946,947,948,949,950,951,952,953,954,955,956,957,958,959,960,961,962,963,964,965,966,967,968,969,970,971,972,973,974,975,976,977,978,979,980,981,982,983,984,985,986,987,988,989,990,991,992,993,994,995,996,997,998,999,1000');
解决方案
- SUBSTRING_INDEX(str, delim, count)：返回字符串 str 在分隔符 delim 出现 count 次前的子字符串
- LENGTH(str)：返回字符串 str 的长度
- REPLACE(str, from_str, to_str)：返回字符串 str，并将所有 from_str 字符串替换为字符串 to_str
- 系统内置表 mysql.help_topic：帮助主题内容表
行转列
SELECT SUBSTRING_INDEX(SUBSTRING_INDEX(你的字段, ',', help_topic_id + 1), ',', -1)
FROM mysql.help_topic, 你的表
WHERE 1=1
AND help_topic_id < LENGTH(你的字段) - LENGTH(REPLACE(你的字段, ',', ''))+1
AND 具体条件
如
SELECT SUBSTRING_INDEX(SUBSTRING_INDEX(hobby, ',', help_topic_id + 1), ',', -1)
FROM mysql.help_topic, person
WHERE 1=1
AND help_topic_id < LENGTH(hobby) - LENGTH(REPLACE(hobby, ',', ''))+1
AND id=3
效果
缺点：
- 需要有权限调用 mysql.help_topic 表
- mysql.help_topic 表不可为空
- mysql.help_topic 表的自增 id，最大值为659，若逗号个数大于该值，需要自己单独处理
解决办法：任意找一个可读表，只需要 id 是从 0 或 1 开始的自然数序列，便可替代 mysql.help_topic 表
统计长度
逗号数量
SELECT *, LENGTH(你的字段) - LENGTH(REPLACE(你的字段, ',', ''))
FROM 你的表
元素数量
SELECT *, LENGTH(你的字段) - LENGTH(REPLACE(你的字段, ',', '')) + 1
FROM 你的表
如
SELECT *, LENGTH(hobby) - LENGTH(REPLACE(hobby, ',', '')) AS '逗号数量', LENGTH(hobby) - LENGTH(REPLACE(hobby, ',', '')) + 1 AS '元素数量'
FROM person
效果
TODO：创建函数
How to split the name string in mysql?
MySQL 字符串拆分操作(含分隔符的字符串截取)
遇到的坑
mysql.help_topic表无权限使用解决方法
参考文献
- MySQL Manual String Functions and Operators
- MySQL字符串函数和操作符
- mysql字符串拆分实现split功能
- MySQL——字符串拆分（含分隔符的字符串截取）
- How to split the name string in mysql?
- How to split and search in comma-separated string in MySQL
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