What is the difference between single and double quotes in SQL?

Question

What is the difference between single quotes and double quotes in SQL?

Answer 1

Single quotes are used to wrap around strings so that they are identified accordingly. Double quotes, depending on the database, often are interpreted as database component identifies. For example, if you want to select all rows from table 'DATA_SOURCE' where column A equals the phrase 'This is a string', you would write statement 1 below. If your column name had a space in it (e.g. "My Column", you would use double quotes to identify the whole name.

--1)

SELECT * FROM DATA_SOURCE WHERE A = 'This is a string';

--2)

SELECT * FROM DATA_SOURCE WHERE "My Column" = 'This is a string';

Answer 2

Double quotes are never used. Text and dates must be inside single quotation marks.