Transform SQL insert script into CSV format

Question

I'm looking for an awk command, or similar tool, to transform standard well formatted SQL insert script into csv file.
By standard I mean there is no database vendor specific stuff anywhere.
By well formatted I mean the case where each line of the sql script has a full column set to insert, even if there are NULLs. Also the order of fields to insert is the same.
Sample input SQL script:

INSERT INTO tbl VALUES (1, 'asd', 923123123, 'zx');
INSERT INTO tbl VALUES (1, NULL, 923123123, 'zxz');
INSERT INTO tbl VALUES (3, 'asd3', 923123123, NULL);

Optionally:

INSERT INTO tbl (colA, colB, colC, colD) VALUES (1, 'asd', 923123123, 'zx');

Expected output should be a csv file:

1,'asd',923123123,'zx'
1,,923123123,'zxz'
3,'asd3',923123123,

Looking for a performance efficient solution.

Answer 1

$ awk -F' *[(),]+ *' -v OFS=, '{for (i=2;i<NF;i++) printf "%s%s", ($i=="NULL"?"":$i), (i<(NF-1)?OFS:ORS)}' file
1,'asd',923123123,'zx'
1,,923123123,'zxz'
3,'asd3',923123123,

I'd recommend you test all potential solutions with this input:

$ cat file
INSERT INTO tbl VALUES (1, NULL, 923123123, 'foo NULL bar');

$ awk -F' *[(),]+ *' -v OFS=, '{for (i=2;i<NF;i++) printf "%s%s", ($i=="NULL"?"":$i), (i<(NF-1)?OFS:ORS)}' file
1,,923123123,'foo NULL bar'

to make sure the string NULL and blank chars are not deleted when they appear as part of a literal string.

Answer 2

Try this with GNU grep and sed:

grep -oP '\(\K[^)]*(?=\);)' file | sed 's/NULL//g;s/ //g'

Output from all four lines:

1,'asd',923123123,'zx'
1,,923123123,'zxz'
3,'asd3',923123123,
1,'asd',923123123,'zx'

or only with GNU sed:

sed 's/.*(\([^)]*\));/\1/;s/NULL//g;s/ //g' file

Output from all four lines:

1,'asd',923123123,'zx'
1,,923123123,'zxz'
3,'asd3',923123123,
1,'asd',923123123,'zx'