This is personal study note
Copyright and original reference:
https://www.youtube.com/watch?v=SLaQHVZXDiE&list=PLVsNizTWUw7HhYtI-4GGmlJ5yxNdwNI_X
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ELT: "second position one" is returned
FIELD: "둘" is located in second position
FIND_IN_SET: "둘" is located in second position by delimeter of ,
INSTR: "둘" is located in 3rd position from "하나둘셋"
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"AA" 16 -> 2
100 10 -> 8
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number of selected rows
number of updated rows