Some simple usage of substr instr in Oracle

Select substr (memo, (instr (memo, ':',-1,1) + 1) from sfa_order_item where trunc (gmt_modified) = trunc (sysdate)

I personally understand some simple subtr usage

Substr ('field name', 3) Here it means to extract this field from the third digit until the end. Of course, if the following number is the same as the length of this field, it is null.

Some simple instr usage

(Instr (memo, ':',-1, 1) + 1)

Instr pulls out the last memo:-1, which means to get the first one from the end. Then, get the first one and their length.

Then substr is intercepted from the specific position.