The reason is, that first the Java compiler interprets the two \\ characters as an escaped Java String character . After the Java compiler is done, only one \ is left, as \\ means the character \ . The string thus looks like this: \.5 Mar 2019
Read moreCan we use regex in substring?
REGEXP_SUBSTR extends the functionality of the SUBSTR function by letting you search a string for a regular expression pattern . It is also similar to REGEXP_INSTR , but instead of returning the position of the substring, it returns the substring itself.
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