Special SQL Character Processing

If there are no restrictions on user input, special characters must be converted.
If you do not change the single quotes, a database error may occur, or even cause a system crash.
However, the avoidance method is very simple. You only need to convert single quotes ['] into two single quotes.
Example: Select * From TBL where Col = 'abc''' def ';
Fuzzy query statements do not produce SQL errors, but cannot be retrieved if they are not avoided.
The Avoidance Method is more complex than single quotes. Escape characters are required. Convert [%] to [\ %] and [_] to [\ _],
Then add [escape.
Example: Select * From TBL where Col like 'abc \ % \ _ % 'escape '\';
※The last % is a wildcard.
If you are a Japanese project, [%], [_],
These two full-width characters are also processed as half-width wildcards.
Therefore, the full-width [%] and [_] must be transformed during conversion.
Example: Select * From TBL where Col like 'abc \ % \ _ % 'escape '\';
It seems like this is over, but don't forget that there are also escape characters. In case you enter the escape characters,
An SQL error occurs during the above processing. Therefore, escape characters must be transformed. The conversion method is to convert [\] to [\].

Example: Select * From TBL where Col like 'abc \ % \ _ % 'escape '\';
The preceding operations are applicable to common data types, such as char and varchar2.
If nchar or nvarchar2 appears, the above processing will result in a ORA-01425 error.

If you change to the following syntax, A ORA-01424 error occurs.
Select * From TBL where Col like '% \ _ %' escape to_nchar ('\')
Which of the following statements is true?
Select * From TBL where Col likec '% \ _ %' escape to_nchar ('\')

The last note is that every like should write an escape statement.
Example:
Select * From TBL
Where col1 like '% \ _ %' escape '\' or col2 like '% \ _ %' escape '\'
Create Table # temp (charcater varchar (50 ))
Insert into # temp
Values
('Werwerweerwe [werwe] werwerwer ')
Insert into # temp
Values
('Werwerweerwe [zzzzzzzzzz ')
Insert into # temp
Values
('Werwerweerwe] zzzzzzzzzz ')

Select * from # temp where charcater like '%] %'
Select * from # temp where charcater like '% [] %'

If you query '[', then like should be followed by [[], and ']', then it will be written directly]