blob handle about sqlite_modern_cpp HOT 2 CLOSED

@alext234

I found this.
http://www.sqlite.org/lang_corefunc.html#substr

substr(X,Y,Z)
substr(X,Y)

The substr(X,Y,Z) function returns a substring of input string X that begins with the Y-th character and which is Z characters long. If Z is omitted then substr(X,Y) returns all characters through the end of the string X beginning with the Y-th. The left-most character of X is number 1. If Y is negative then the first character of the substring is found by counting from the right rather than the left. If Z is negative then the abs(Z) characters preceding the Y-th character are returned. If X is a string then characters indices refer to actual UTF-8 characters. If X is a BLOB then the indices refer to bytes.

So something like this should work (i have not tested this, it's just my guess)

db << "CREATE TABLE person (name TEXT, numbers BLOB);";
db << "INSERT INTO person VALUES (?, ?)" << "bob" << vector<int> { 1, 2, 3, 4, 5, 6, 7};       
vector<int> numbers_bob;
db << "SELECT SUBSTR(numbers,?,?) from person where name = ?;"
    << 8 /* offset */ << 12 /* count */ <<  "bob" >> numbers_bob;
// numbers_bob should become { 3, 4, 5}

Alex if this or something similar worked for you please add your code here.
If SUBSTR didn't help, update the issue and we will think of another way to address this :-)

from sqlite_modern_cpp.

@aminroosta substr works fine for me. Thanks 👍

from sqlite_modern_cpp.