目錄
LOAD 基本背景
我們在數據庫運維過程中難免會涉及到需要對文本數據進行處理,並導入到數據庫中,本文整理了一些導入導出時常見的場景進行示例演示
LOAD 基礎參數
文章後續示例均使用以下命令導出的csv格式樣例數據(以
,逗號做分隔符,以"雙引號作爲界定符)
-- 導出基礎參數
select * into outfile '/data/mysql/3306/tmp/employees.txt'
character set utf8mb4
fields terminated by ','
enclosed by '"'
lines terminated by '\n'
from employees.employees limit 10;
-- 導入基礎參數
load data infile '/data/mysql/3306/tmp/employees.txt'
replace into table demo.emp
character set utf8mb4
fields terminated by ','
enclosed by '"'
lines terminated by '\n'
...
LOAD 示例數據及示例表結構
以下爲示例數據,表結構及對應關係信息
-- 導出的文件數據內容
[root@10-186-61-162 tmp]# cat employees.txt
"10001","1953-09-02","Georgi","Facello","M","1986-06-26"
"10002","1964-06-02","Bezalel","Simmel","F","1985-11-21"
"10003","1959-12-03","Parto","Bamford","M","1986-08-28"
"10004","1954-05-01","Chirstian","Koblick","M","1986-12-01"
"10005","1955-01-21","Kyoichi","Maliniak","M","1989-09-12"
"10006","1953-04-20","Anneke","Preusig","F","1989-06-02"
"10007","1957-05-23","Tzvetan","Zielinski","F","1989-02-10"
"10008","1958-02-19","Saniya","Kalloufi","M","1994-09-15"
"10009","1952-04-19","Sumant","Peac","F","1985-02-18"
"10010","1963-06-01","Duangkaew","Piveteau","F","1989-08-24"
-- 示例表結構
SQL > desc demo.emp;
+-------------+---------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+-------------+---------------+------+-----+---------+-------+
| emp_no | int | NO | PRI | NULL | |
| birth_date | date | NO | | NULL | |
| first_name | varchar(16) | NO | | NULL | |
| last_name | varchar(16) | NO | | NULL | |
| fullname | varchar(32) | YES | | NULL | | -- 表新增字段,導出數據文件中不存在
| gender | enum('M','F') | NO | | NULL | |
| hire_date | date | NO | | NULL | |
| modify_date | datetime | YES | | NULL | | -- 表新增字段,導出數據文件中不存在
| delete_flag | char(1) | YES | | NULL | | -- 表新增字段,導出數據文件中不存在
+-------------+---------------+------+-----+---------+-------+
-- 導出的數據與字段對應關係
emp_no birth_date first_name last_name gender hire_date
"10001" "1953-09-02" "Georgi" "Facello" "M" "1986-06-26"
"10002" "1964-06-02" "Bezalel" "Simmel" "F" "1985-11-21"
"10003" "1959-12-03" "Parto" "Bamford" "M" "1986-08-28"
"10004" "1954-05-01" "Chirstian" "Koblick" "M" "1986-12-01"
"10005" "1955-01-21" "Kyoichi" "Maliniak" "M" "1989-09-12"
"10006" "1953-04-20" "Anneke" "Preusig" "F" "1989-06-02"
"10007" "1957-05-23" "Tzvetan" "Zielinski" "F" "1989-02-10"
"10008" "1958-02-19" "Saniya" "Kalloufi" "M" "1994-09-15"
"10009" "1952-04-19" "Sumant" "Peac" "F" "1985-02-18"
"10010" "1963-06-01" "Duangkaew" "Piveteau" "F" "1989-08-24"
LOAD 場景示例
場景1. LOAD 文件中的字段比數據表中的字段多
只需要文本文件中部分數據導入到數據表中
-- 臨時創建2個字段的表結構
SQL > create table emp_tmp select emp_no,hire_date from emp;
SQL > desc emp_tmp;
+-----------+------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+-----------+------+------+-----+---------+-------+
| emp_no | int | NO | | NULL | |
| hire_date | date | NO | | NULL | |
+-----------+------+------+-----+---------+-------+
-- 導入數據語句
load data infile '/data/mysql/3306/tmp/employees.txt'
replace into table demo.emp_tmp
character set utf8mb4
fields terminated by ','
enclosed by '"'
lines terminated by '\n'
(@C1,@C2,@C3,@C4,@C5,@C6) -- 該部分對應employees.txt文件中6列數據
-- 只對導出數據中指定的2個列與表中字段做匹配,mapping關係指定的順序不影響導入結果
set hire_date=@C6,
emp_no=@C1;
-- 導入數據結果示例
SQL > select * from emp_tmp;
+--------+------------+
| emp_no | hire_date |
+--------+------------+
| 10001 | 1986-06-26 |
| 10002 | 1985-11-21 |
| 10003 | 1986-08-28 |
| 10004 | 1986-12-01 |
| 10005 | 1989-09-12 |
| 10006 | 1989-06-02 |
| 10007 | 1989-02-10 |
| 10008 | 1994-09-15 |
| 10009 | 1985-02-18 |
| 10010 | 1989-08-24 |
+--------+------------+
10 rows in set (0.0016 sec)
場景2. LOAD 文件中的字段比數據表中的字段少
表字段不僅包含文本文件中所有數據,還包含了額外的字段
-- 導入數據語句
load data infile '/data/mysql/3306/tmp/employees.txt'
replace into table demo.emp
character set utf8mb4
fields terminated by ','
enclosed by '"'
lines terminated by '\n'
(@C1,@C2,@C3,@C4,@C5,@C6) -- 該部分對應employees.txt文件中6列數據
-- 將文件中的字段與表中字段做mapping對應,表中多出的字段不做處理
set emp_no=@C1,
birth_date=@C2,
first_name=@C3,
last_name=@C4,
gender=@C5,
hire_date=@C6;
場景3. LOAD 生成自定義字段數據
從場景2的驗證可以看到,emp表中新增的字段
fullname,modify_date,delete_flag字段在導入時並未做處理,被置爲了NULL值,如果需要對其進行處理,可在LOAD時通過MySQL支持的函數或給定固定值自行定義數據,對於文件中存在的字段也可做函數處理,結合導入導出,實現簡單的ETL功能,如下所示
-- 導入數據語句
load data infile '/data/mysql/3306/tmp/employees.txt'
replace into table demo.emp
character set utf8mb4
fields terminated by ','
enclosed by '"'
lines terminated by '\n'
(@C1,@C2,@C3,@C4,@C5,@C6) -- 該部分對應employees.txt文件中6列數據
-- 以下部分明確對錶中字段與數據文件中的字段做Mapping關係,不存在的數據通過函數處理生成(也可設置爲固定值)
set emp_no=@C1,
birth_date=@C2,
first_name=upper(@C3), -- 將導入的數據轉爲大寫
last_name=lower(@C4), -- 將導入的數據轉爲小寫
fullname=concat(first_name,' ',last_name), -- 對first_name和last_name做拼接
gender=@C5,
hire_date=@C6 ,
modify_date=now(), -- 生成當前時間數據
delete_flag=if(hire_date<'1988-01-01','Y','N'); -- 對需要生成的值基於某一列做條件運算
場景4. LOAD 定長數據
定長數據的特點如下所示,可以使用函數取出字符串中固定長度來生成指定列數據
SQL > select
c1 as sample_data,
substr(c1,1,3) as c1,
substr(c1,4,3) as c2,
substr(c1,7,2) as c3,
substr(c1,9,5) as c4,
substr(c1,14,3) as c5,
substr(c1,17,3) as c6 from t1
*************************** 1. row ***************************
sample_data: ABC餘振興CDMySQLEFG數據庫
c1: ABC
c2: 餘振興
c3: CD
c4: MySQL
c5: EFG
c6: 數據庫
定長數據導入需要明確每列數據佔用的字符個數,以下直接使用rpad對現有的表數據填充空格的方式生成定長數據用作示例使用
-- 生成定長數據
SQL > select
concat(rpad(emp_no,10,' '),
rpad(birth_date,19,' '),
rpad(first_name,14,' '),
rpad(last_name,16,' '),
rpad(gender,2,' '),
rpad(hire_date,19,' ')) as fixed_length_data
from employees.employees limit 10;
+----------------------------------------------------------------------------------+
| fixed_length_data |
+----------------------------------------------------------------------------------+
| 10001 1953-09-02 Georgi Facello M 1986-06-26 |
| 10002 1964-06-02 Bezalel Simmel F 1985-11-21 |
| 10003 1959-12-03 Parto Bamford M 1986-08-28 |
| 10004 1954-05-01 Chirstian Koblick M 1986-12-01 |
| 10005 1955-01-21 Kyoichi Maliniak M 1989-09-12 |
| 10006 1953-04-20 Anneke Preusig F 1989-06-02 |
| 10007 1957-05-23 Tzvetan Zielinski F 1989-02-10 |
| 10008 1958-02-19 Saniya Kalloufi M 1994-09-15 |
| 10009 1952-04-19 Sumant Peac F 1985-02-18 |
| 10010 1963-06-01 Duangkaew Piveteau F 1989-08-24 |
+----------------------------------------------------------------------------------+
-- 導出定長數據
select
concat(rpad(emp_no,10,' '),
rpad(birth_date,19,' '),
rpad(first_name,14,' '),
rpad(last_name,16,' '),
rpad(gender,2,' '),
rpad(hire_date,19,' ')) as fixed_length_data
into outfile '/data/mysql/3306/tmp/employees_fixed.txt'
character set utf8mb4
lines terminated by '\n'
from employees.employees limit 10;
-- 導出數據示例
[root@10-186-61-162 tmp]# cat employees_fixed.txt
10001 1953-09-02 Georgi Facello M 1986-06-26
10002 1964-06-02 Bezalel Simmel F 1985-11-21
10003 1959-12-03 Parto Bamford M 1986-08-28
10004 1954-05-01 Chirstian Koblick M 1986-12-01
10005 1955-01-21 Kyoichi Maliniak M 1989-09-12
10006 1953-04-20 Anneke Preusig F 1989-06-02
10007 1957-05-23 Tzvetan Zielinski F 1989-02-10
10008 1958-02-19 Saniya Kalloufi M 1994-09-15
10009 1952-04-19 Sumant Peac F 1985-02-18
10010 1963-06-01 Duangkaew Piveteau F 1989-08-24
-- 導入定長數據
load data infile '/data/mysql/3306/tmp/employees_fixed.txt'
replace into table demo.emp
character set utf8mb4
fields terminated by ','
enclosed by '"'
lines terminated by '\n'
(@row) -- 對一行數據定義爲一個整體
set emp_no = trim(substr(@row,1,10)),-- 使用substr取前10個字符,並去除頭尾空格數據
birth_date = trim(substr(@row,11,19)),-- 後續字段以此類推
first_name = trim(substr(@row,30,14)),
last_name = trim(substr(@row,44,16)),
fullname = concat(first_name,' ',last_name), -- 對first_name和last_name做拼接
gender = trim(substr(@row,60,2)),
hire_date = trim(substr(@row,62,19)),
modify_date = now(),
delete_flag = if(hire_date<'1988-01-01','Y','N'); -- 對需要生成的值基於某一列做條件運算
LOAD 總結
-
默認情況下導入的順序以文本文件
列-從左到右,行-從上到下的順序導入 -
如果表結構和文本數據不一致,建議將文本文件中的各列依次順序編號並與表中字段建立mapping關係,以防數據導入到錯誤的字段
-
對於待導入的文本文件較大的場景,建議將文件
按行拆分爲多個小文件,如用split拆分 -
對文件導入後建議執行以下語句驗證導入的數據是否有
Warning,ERROR以及導入的數據量-
GET DIAGNOSTICS @p1=NUMBER,@p2=ROW_COUNT; -
select @p1 AS ERROR_COUNT,@p2 as ROW_COUNT;
-
-
文本文件數據與表結構存在過大的差異或數據需要做清洗轉換,建議還是用專業的ETL工具或先粗略導入MySQL中再進行加工轉換處理