Question

SQLDF newbie here.

I have a data frame which has about 15,000 rows and 1 column.
The data looks like:

cars
autocar
carsinfo
whatisthat
donnadrive
car
telephone
...

I wanted to use the package sqldf to loop through the column and
pick all values which contain “car” anywhere in their value.
However, the following code generates an error.

> sqldf("SELECT Keyword FROM dat WHERE Keyword="car")
Error: unexpected symbol in "sqldf("SELECT Keyword FROM dat WHERE Keyword="car"

There is no unexpected symbol, so I’m not sure whats wrong.

so first, I want to know all the values which contain ‘car’.
then I want to know only those values which contain just ‘car’ by itself.

Can anyone help.

EDIT:

allright, there was an unexpected symbol, but it only gives me just car and not every
row which contains ‘car’.

> sqldf("SELECT Keyword FROM dat WHERE Keyword='car'")
  Keyword
1     car

Answer 1

Using = will only return exact matches.

You should probably use the like operator combined with the wildcards % or _. The % wildcard will match multiple characters, while _ matches a single character.

Something like the following will find all instances of car, e.g. “cars”, “motorcar”, etc:

sqldf("SELECT Keyword FROM dat WHERE Keyword like '%car%'")

And the following will match “car” or “cars”:

sqldf("SELECT Keyword FROM dat WHERE Keyword like 'car_'")