SQLite Forum

I have compared string functions in 5 different RDBMS: **PostgreSQL**, **MySQL**, **Oracle**, **SQL Server** and **SQLite**, and also in the [ANSI SQL Standard](https://en.wikipedia.org/wiki/SQL#Standardization_history). There are large differences among different RDBMS, and I propose to reduce them a little bit.

The SQL Standard defines, among others, these functions operating on text strings:

      TRIM([[LEADING|TRAILING|BOTH] [c] FROM] s)
      SUBSTRING(s FROM start [FOR length])
      POSITION(s2 IN s)

They are already implemented by PostgreSQL and MySQL. Oracle implements only `TRIM` function according to SQL Standard.

I propose to implement these 3 functions in Oracle, SQL Server and SQLite as well. However, I don't know if the support of the LEADING, TRAILING, BOTH, FROM, FOR, IN keywords in the list of function parameters will not be a problem in SQLite.

Currently, SQL Server implements the following functions that work identically to the SQL Standard:

      [L|R]TRIM([c FROM] s)
      SUBSTRING(s, start, length)
      CHARINDEX(s2, s)

SQLite implements the following functions that work identically to the SQL Standard:

      [L|R]TRIM(s [,c])
      SUBSTR(s, start [,length])
      INSTR(s, s2)

and Oracle implements the following functions that work identically to the SQL Standard:

      SUBSTR(s, start [,length])
      INSTR(s, s2)

For more information about comparing implementations of the scalar functions, click here: [https://github.com/iwis/SQL-notes/blob/master/Functions.txt](https://github.com/iwis/SQL-notes/blob/master/Functions.txt)