Oracle: single quote in string

Apostrophe/single quote at start of string

When the apostrophe/single quote is at the start of the string, you need to enter 3 single quotes for Oracle to display a quote symbol. For example:

SELECT '''Hi There'
FROM dual;

would return

'Hi There

Apostrophe/single quote in the middle of a string

When the apostrophe/single quote is in the middle of the string, you need to enter 2 single quotes for Oracle to display a quote symbol. For example:

SELECT 'He''s always the first to arrive'
FROM dual;

would return

He's always the first to arrive

Apostrophe/single quote at the end of a string

When the apostrophe/single quote is at the end of a string, you need to enter 3 single quotes for Oracle to display a quote symbol. For example:

SELECT 'Smiths'''
FROM dual;

would return

Smiths'

Apostrophe/single quote in a concatenated string

If you were to concatenate an apostrophe/single quote in a string, you need to enter 4 single quotes for Oracle to display a quote symbol. For example:

SELECT 'There' || '''' || 's Henry'
FROM dual;

would return

There's Henry

Reference: http://www.techonthenet.com/oracle/questions/quotes.php