Archive for February 2nd, 2012

Quote Marks in Parameters in SQL

Often in SQL examples you will see quote marks around a string that is being operated upon. Generally, a straight string is not often used in general practice. It is more likely to be a variable and more likely yet to be a column. Having or not having quote marks can make a huge difference in the results given by a function. We will use the LEFT() function as an example. The left function is a way to get the leftmost characters from a
string.

SELECT LEFT(‘string’, number_of_characters)

To get the 7 left-most characters from a specific column in every row of a table the following would work:

SELECT LEFT(name, 7) FROM fict_chars

It should be noted for this and for other functions that if the string is in single quotes that SQL will see it as a literal string. If it is not, SQL will see it as a column. Thus, had we used ‘name’, the result would have been “name” for each row, and not the actual name drawn from the specified column.

 

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