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1# Project:M36 CSV Import/Export
3Project:M36's `tutd` console supports the import and export of CSV files as a lowest-common denominator format for moving data. Because the CSV file format does not support all the features of Project:M36- most notably, nested relations- not all relation variables can be marshalled to-and-from CSV files.
5## CSV Export
7If a relation variable cannot be exported due to data types which are not supported by the CSV format- such as with a nested relation- then Project:M36 throws an error rather than export a partial file.
9### Example Export
11```
12TutorialD (master/main): :importexample cjdate
13TutorialD (master/main): :exportcsv s "/tmp/csv"
14```
15```
16$ cat /tmp/csv
17s#,sname,status,city
18S2,Jones,10,Paris
19S1,Smith,20,London
20S4,Clark,20,London
21S5,Adams,30,Athens
22S3,Blake,30,Paris
23```
25## CSV Import
27An import is equivalent to an insert and does not replace the target relation variable.
29Because relations do not have a natural ordering for their attributes, the CSV file to import must contain a header row which matches the names of attributes.
31If a value in the CSV file cannot be converted to the expected type (determined by the existing relation attributes), then the entire import is aborted rather than perform a partial import.
33### Example Import
34```
35$ cat /tmp/csv
36s#,sname,status,city
37S6,Samson,100,New York
38```
39```
40TutorialD (master/main): :importexample cjdate
41TutorialD (master/main): :showexpr s
42┌──────────┬────────┬───────────┬───────────────┐
43│city::Text│s#::Text│sname::Text│status::Integer│
44├──────────┼────────┼───────────┼───────────────┤
45│"Paris" │"S2" │"Jones" │10 │
46│"Paris" │"S3" │"Blake" │30 │
47│"London" │"S4" │"Clark" │20 │
48│"London" │"S1" │"Smith" │20 │
49│"Athens" │"S5" │"Adams" │30 │
50└──────────┴────────┴───────────┴───────────────┘
51TutorialD (master/main): :importcsv "/tmp/csv" s
52TutorialD (master/main): :showexpr s
53┌──────────┬────────┬───────────┬───────────────┐
54│city::Text│s#::Text│sname::Text│status::Integer│
55├──────────┼────────┼───────────┼───────────────┤
56│"Paris" │"S3" │"Blake" │30 │
57│"London" │"S4" │"Clark" │20 │
58│"New York"│"S6" │"Samson" │100 │
59│"Athens" │"S5" │"Adams" │30 │
60│"London" │"S1" │"Smith" │20 │
61│"Paris" │"S2" │"Jones" │10 │
62└──────────┴────────┴───────────┴───────────────┘
63```
65Note that relations do not have ordering, thus, no ordering from the CSV file is preserved.