MySQL数据库 Load Data 多种用法

时间：2022-04-20 17:51:35

MySQL Load Data 的多种用法

 

一、LOAD 基本背景

我们在数据库运维过程中难免会涉及到需要对文本数据进行处理，并导入到数据库中，本文整理了一些导入导出时常见的场景进行示例演示。

二、LOAD 基础参数

文章后续示例均使用以下命令导出的 csv 格式样例数据(以 , 逗号做分隔符，以 " 双引号作为界定符)

  1. -- 导出基础参数
  2. select * into outfile '/data/mysql/3306/tmp/employees.txt'
  3. character set utf8mb4
  4. fields terminated by ','
  5. enclosed by '"'
  6. lines terminated by ' '
  7. from employees.employees limit 10;
  8.  
  9. -- 导入基础参数
  10. load data infile '/data/mysql/3306/tmp/employees.txt'
  11. replace into table demo.emp
  12. character set utf8mb4
  13. fields terminated by ','
  14. enclosed by '"'
  15. lines terminated by ' '
  16. ...

三、LOAD 示例数据及示例表结构

以下为示例数据，表结构及对应关系信息

  1. -- 导出的文件数据内容
  2. [root@10-186-61-162 tmp]# cat employees.txt
  3. "10001","1953-09-02","Georgi","Facello","M","1986-06-26"
  4. "10002","1964-06-02","Bezalel","Simmel","F","1985-11-21"
  5. "10003","1959-12-03","Parto","Bamford","M","1986-08-28"
  6. "10004","1954-05-01","Chirstian","Koblick","M","1986-12-01"
  7. "10005","1955-01-21","Kyoichi","Maliniak","M","1989-09-12"
  8. "10006","1953-04-20","Anneke","Preusig","F","1989-06-02"
  9. "10007","1957-05-23","Tzvetan","Zielinski","F","1989-02-10"
  10. "10008","1958-02-19","Saniya","Kalloufi","M","1994-09-15"
  11. "10009","1952-04-19","Sumant","Peac","F","1985-02-18"
  12. "10010","1963-06-01","Duangkaew","Piveteau","F","1989-08-24"
  13.  
  14. -- 示例表结构
  15. SQL > desc demo.emp;
  16. +-------------+---------------+------+-----+---------+-------+
  17. | Field | Type | Null | Key | Default | Extra |
  18. +-------------+---------------+------+-----+---------+-------+
  19. | emp_no | int | NO | PRI | NULL | |
  20. | birth_date | date | NO | | NULL | |
  21. | first_name | varchar(16) | NO | | NULL | |
  22. | last_name | varchar(16) | NO | | NULL | |
  23. | fullname | varchar(32) | YES | | NULL | | -- 表新增字段,导出数据文件中不存在
  24. | gender | enum('M','F') | NO | | NULL | |
  25. | hire_date | date | NO | | NULL | |
  26. | modify_date | datetime | YES | | NULL | | -- 表新增字段,导出数据文件中不存在
  27. | delete_flag | char(1) | YES | | NULL | | -- 表新增字段,导出数据文件中不存在
  28. +-------------+---------------+------+-----+---------+-------+
  29.  
  30. -- 导出的数据与字段对应关系
  31. emp_no birth_date first_name last_name gender hire_date
  32. "10001" "1953-09-02" "Georgi" "Facello" "M" "1986-06-26"
  33. "10002" "1964-06-02" "Bezalel" "Simmel" "F" "1985-11-21"
  34. "10003" "1959-12-03" "Parto" "Bamford" "M" "1986-08-28"
  35. "10004" "1954-05-01" "Chirstian" "Koblick" "M" "1986-12-01"
  36. "10005" "1955-01-21" "Kyoichi" "Maliniak" "M" "1989-09-12"
  37. "10006" "1953-04-20" "Anneke" "Preusig" "F" "1989-06-02"
  38. "10007" "1957-05-23" "Tzvetan" "Zielinski" "F" "1989-02-10"
  39. "10008" "1958-02-19" "Saniya" "Kalloufi" "M" "1994-09-15"
  40. "10009" "1952-04-19" "Sumant" "Peac" "F" "1985-02-18"
  41. "10010" "1963-06-01" "Duangkaew" "Piveteau" "F" "1989-08-24"

四、LOAD 场景示例

场景1. LOAD 文件中的字段比数据表中的字段多

只需要文本文件中部分数据导入到数据表中

  1. -- 临时创建2个字段的表结构
  2. SQL > create table emp_tmp select emp_no,hire_date from emp;
  3. SQL > desc emp_tmp;
  4. +-----------+------+------+-----+---------+-------+
  5. | Field | Type | Null | Key | Default | Extra |
  6. +-----------+------+------+-----+---------+-------+
  7. | emp_no | int | NO | | NULL | |
  8. | hire_date | date | NO | | NULL | |
  9. +-----------+------+------+-----+---------+-------+
  10.  
  11. -- 导入数据语句
  12. load data infile '/data/mysql/3306/tmp/employees.txt'
  13. replace into table demo.emp_tmp
  14. character set utf8mb4
  15. fields terminated by ','
  16. enclosed by '"'
  17. lines terminated by ' '
  18. (@C1,@C2,@C3,@C4,@C5,@C6) -- 该部分对应employees.txt文件中6列数据
  19. -- 只对导出数据中指定的2个列与表中字段做匹配,mapping关系指定的顺序不影响导入结果
  20. set hire_date=@C6,
  21. emp_no=@C1;
  22.  
  23. -- 导入数据结果示例
  24. SQL > select * from emp_tmp;
  25. +--------+------------+
  26. | emp_no | hire_date |
  27. +--------+------------+
  28. | 10001 | 1986-06-26 |
  29. | 10002 | 1985-11-21 |
  30. | 10003 | 1986-08-28 |
  31. | 10004 | 1986-12-01 |
  32. | 10005 | 1989-09-12 |
  33. | 10006 | 1989-06-02 |
  34. | 10007 | 1989-02-10 |
  35. | 10008 | 1994-09-15 |
  36. | 10009 | 1985-02-18 |
  37. | 10010 | 1989-08-24 |
  38. +--------+------------+
  39. 10 rows in set (0.0016 sec)

场景 2. LOAD 文件中的字段比数据表中的字段少

表字段不仅包含文本文件中所有数据,还包含了额外的字段

  1. -- 导入数据语句
  2. load data infile '/data/mysql/3306/tmp/employees.txt'
  3. replace into table demo.emp
  4. character set utf8mb4
  5. fields terminated by ','
  6. enclosed by '"'
  7. lines terminated by ' '
  8. (@C1,@C2,@C3,@C4,@C5,@C6) -- 该部分对应employees.txt文件中6列数据
  9. -- 将文件中的字段与表中字段做mapping对应,表中多出的字段不做处理
  10. set emp_no=@C1,
  11. birth_date=@C2,
  12. first_name=@C3,
  13. last_name=@C4,
  14. gender=@C5,
  15. hire_date=@C6;

MySQL数据库 Load Data 多种用法 

场景3. LOAD 生成自定义字段数据

从场景 2 的验证可以看到，emp 表中新增的字段 fullname,modify_date,delete_flag 字段在导入时并未做处理，被置为了 NULL 值，如果需要对其进行处理，可在 LOAD 时通过 MySQL支持的函数 或给定 固定值 自行定义数据，对于文件中存在的字段也可做函数处理，结合导入导出，实现简单的 ETL 功能，如下所示：

  1. -- 导入数据语句
  2. load data infile '/data/mysql/3306/tmp/employees.txt'
  3. replace into table demo.emp
  4. character set utf8mb4
  5. fields terminated by ','
  6. enclosed by '"'
  7. lines terminated by ' '
  8. (@C1,@C2,@C3,@C4,@C5,@C6) -- 该部分对应employees.txt文件中6列数据
  9.  
  10. -- 以下部分明确对表中字段与数据文件中的字段做Mapping关系,不存在的数据通过函数处理生成(也可设置为固定值)
  11. set emp_no=@C1,
  12. birth_date=@C2,
  13. first_name=upper(@C3), -- 将导入的数据转为大写
  14. last_name=lower(@C4), -- 将导入的数据转为小写
  15. fullname=concat(first_name,' ',last_name), -- 对first_name和last_name做拼接
  16. gender=@C5,
  17. hire_date=@C6 ,
  18. modify_date=now(), -- 生成当前时间数据
  19. delete_flag=if(hire_date<'1988-01-01','Y','N'); -- 对需要生成的值基于某一列做条件运算

MySQL数据库 Load Data 多种用法

场景4. LOAD 定长数据

定长数据的特点如下所示，可以使用函数取出字符串中固定长度来生成指定列数据

  1. SQL > select
  2. c1 as sample_data,
  3. substr(c1,1,3) as c1,
  4. substr(c1,4,3) as c2,
  5. substr(c1,7,2) as c3,
  6. substr(c1,9,5) as c4,
  7. substr(c1,14,3) as c5,
  8. substr(c1,17,3) as c6 from t1
  9.  
  10. *************************** 1. row ***************************
  11. sample_data: ABC余振兴CDMySQLEFG数据库
  12. c1: ABC
  13. c2: 余振兴
  14. c3: CD
  15. c4: MySQL
  16. c5: EFG
  17. c6: 数据库

定长数据导入需要明确每列数据占用的字符个数，以下直接使用 rpad 对现有的表数据填充空格的方式生成定长数据用作示例使用

  1. -- 生成定长数据
  2. SQL > select
  3. concat(rpad(emp_no,10,' '),
  4. rpad(birth_date,19,' '),
  5. rpad(first_name,14,' '),
  6. rpad(last_name,16,' '),
  7. rpad(gender,2,' '),
  8. rpad(hire_date,19,' ')) as fixed_length_data
  9. from employees.employees limit 10;
  10.  
  11. +----------------------------------------------------------------------------------+
  12. | fixed_length_data |
  13. +----------------------------------------------------------------------------------+
  14. | 10001 1953-09-02 Georgi Facello M 1986-06-26 |
  15. | 10002 1964-06-02 Bezalel Simmel F 1985-11-21 |
  16. | 10003 1959-12-03 Parto Bamford M 1986-08-28 |
  17. | 10004 1954-05-01 Chirstian Koblick M 1986-12-01 |
  18. | 10005 1955-01-21 Kyoichi Maliniak M 1989-09-12 |
  19. | 10006 1953-04-20 Anneke Preusig F 1989-06-02 |
  20. | 10007 1957-05-23 Tzvetan Zielinski F 1989-02-10 |
  21. | 10008 1958-02-19 Saniya Kalloufi M 1994-09-15 |
  22. | 10009 1952-04-19 Sumant Peac F 1985-02-18 |
  23. | 10010 1963-06-01 Duangkaew Piveteau F 1989-08-24 |
  24. +----------------------------------------------------------------------------------+
  25.  
  26. -- 导出定长数据
  27. select
  28. concat(rpad(emp_no,10,' '),
  29. rpad(birth_date,19,' '),
  30. rpad(first_name,14,' '),
  31. rpad(last_name,16,' '),
  32. rpad(gender,2,' '),
  33. rpad(hire_date,19,' ')) as fixed_length_data
  34. into outfile '/data/mysql/3306/tmp/employees_fixed.txt'
  35. character set utf8mb4
  36. lines terminated by ' '
  37. from employees.employees limit 10;
  38.  
  39. -- 导出数据示例
  40. [root@10-186-61-162 tmp]# cat employees_fixed.txt
  41. 10001 1953-09-02 Georgi Facello M 1986-06-26
  42. 10002 1964-06-02 Bezalel Simmel F 1985-11-21
  43. 10003 1959-12-03 Parto Bamford M 1986-08-28
  44. 10004 1954-05-01 Chirstian Koblick M 1986-12-01
  45. 10005 1955-01-21 Kyoichi Maliniak M 1989-09-12
  46. 10006 1953-04-20 Anneke Preusig F 1989-06-02
  47. 10007 1957-05-23 Tzvetan Zielinski F 1989-02-10
  48. 10008 1958-02-19 Saniya Kalloufi M 1994-09-15
  49. 10009 1952-04-19 Sumant Peac F 1985-02-18
  50. 10010 1963-06-01 Duangkaew Piveteau F 1989-08-24
  51.  
  52. -- 导入定长数据
  53. load data infile '/data/mysql/3306/tmp/employees_fixed.txt'
  54. replace into table demo.emp
  55. character set utf8mb4
  56. fields terminated by ','
  57. enclosed by '"'
  58. lines terminated by ' '
  59. (@row) -- 对一行数据定义为一个整体
  60. set emp_no = trim(substr(@row,1,10)),-- 使用substr取前10个字符,并去除头尾空格数据
  61. birth_date = trim(substr(@row,11,19)),-- 后续字段以此类推
  62. first_name = trim(substr(@row,30,14)),
  63. last_name = trim(substr(@row,44,16)),
  64. fullname = concat(first_name,' ',last_name), -- 对first_name和last_name做拼接
  65. gender = trim(substr(@row,60,2)),
  66. hire_date = trim(substr(@row,62,19)),
  67. modify_date = now(),
  68. delete_flag = if(hire_date<'1988-01-01','Y','N'); -- 对需要生成的值基于某一列做条件运算

MySQL数据库 Load Data 多种用法

五、LOAD 总结

1.默认情况下导入的顺序以文本文件 列-从左到右，行-从上到下 的顺序导入

2.如果表结构和文本数据不一致，建议将文本文件中的各列依次顺序编号并与表中字段建立 mapping 关系，以防数据导入到错误的字段

3.对于待导入的文本文件较大的场景，建议将文件 按行拆分 为多个小文件，如用 split 拆分

4.对文件导入后建议执行以下语句验证导入的数据是否有 Warning,ERROR 以及导入的数据量

  • GET DIAGNOSTICS @p1=NUMBER,@p2=ROW_COUNT;
  • select @p1 AS ERROR_COUNT,@p2 as ROW_COUNT;

5.文本文件数据与表结构存在过大的差异或数据需要做清洗转换，建议还是用专业的 ETL 工具或先粗略导入 MySQL 中再进行加工转换处理

以上就是 MySQL Load Data 数据的多种用法的详细内容，更多关于MySQL Load Data 的用法的资料请关注服务器之家其它相关文章！,希望大家以后多多支持我们！

原文链接：https://blog.csdn.net/ActionTech/article/details/115212340

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