Use of join in Shell programming _ programming

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JoinSimilar to the Join method in db, there is also a left join right join INNER JOIN, etc.
Specifies the way the join is specified by the parameter-A.
-A1 represents a row that does not match in the first file, that is, a LEFT join
-A2 represents a row that does not match in the second file, that is right join
-O 1.1 2.1-o is an output parameter, 1.1 indicates that the first column of the first file is output; 2.1 indicates that the first column of the second file is output
-T ' | ' is a separator parameter that specifies | as the field separator
-J 1.1 2.1-j is a field parameter that represents a connection, where the first column of the first file and the first column of the second file are associated
Look at the following examples of operations:
The contents of the file Test1 are:
001:002
002:shdha
003:sjdh
004:dhahh
The contents of the file Test2 are:
001:aaaa
002:bbbb
008:hhhhh

Using the command join-t ': ' test1 test2 output is:
001:002:aaaa
002:shdha:bbbb
Using the command join-a1-t ': ' test1 test2 output is:
001:002:aaaa
002:shdha:bbbb
003:sjdh
004:dhahh
Using the command join-a1-a2-t ': ' test1 test2 output is:
001:002:aaaa
002:shdha:bbbb
003:sjdh
004:dhahh
008:hhhhh
Use the command join-o 1.2-t ': ' test1 test2 output is:
002
Shdha
Also see examples of output if multiple identical keys exist
# Cat AA
123|11|aaaaa
124|12|abasf
125|12|aaccc
126|13|ccccc
127|14|ccvvv
128|17|vgfgd
# Cat BB
12|aaa
12|ddd
13|aaa
14|aaa
Command join-2 1-1 2-t ' | '-o 1.1,1.2,1.3 aa BB generation
124|12|ABASF #多次输出12这个KEY
124|12|abasf
125|12|aaccc
125|12|aaccc
126|13|ccccc
127|14|ccvvv