What problems will Oracle substr encounter when running?

Do you notice that during system cutover, we use stored procedures to convert data. When using Oracle substr, we generally encounter the following four problems. 1. Define A variable A as varchar2 (30); 2. assign A value to variable A using substr (xx,) from A table; the content of the xx field is A mixture of Chinese and English;

3. error: the system prompts that the string buffer area is insufficient;

4. Use max (length (xx) to return 20;

I checked it for half a day and confused it for half a day.

I talked with another database developer and found the problem:

1. length, Oracle substr are the number of calculated content, which cannot reflect the number of bytes;

2. If you want to know whether a field can be inserted into a field, use lengthB to calculate the number of bytes;

3. A well-known sentence: a Chinese character contains two bytes;

4. Experience: communicate with others more. Don't be afraid of shame. You must be a teacher for the three!

The above content is an introduction to the problems encountered by Oracle substr. I hope you will have some gains.