'As' and 'Like'

Here is my question:- "I’ve worked as a dog" or "I’ve worked like a dog." What is the difference between as and like?

As and like are used in a number of different ways and can be different parts of speech.

1. 'as' and 'like' - prepositions:

As refers to something or someone's appearance or function. Consider the following examples:

   'Before I became a teacher I worked as a waiter.'
   'I'm going to the fancy dress party as Superman.'
   'The sea can be used as a source of energy.'The expression 'I've been working as a dog' sounds unusual because it suggests that you were doing the work of a dog! 

Like has the meaning 'similar to' and is used when comparing things. Look at these examples:
   'I’ve been working like a dog.'
   'She looks a bit like her brother.'
   'Just like you, I’m always a bit wary of large dogs.'

The expression 'I've been working like a dog' is idiomatic and means that you have been working very hard. Note that we can use adverbs of degree, such as just, very, quite, not much, not at all, a bit, etc, to modify like:
   'He’s very serious – not at all like his father, perhaps more like his mother at times.

2. 'as' and 'like' - conjunctions:

As and like can also be used as conjunctions:
As means 'in the same way that'. Consider the following:
   'I always drink tea without milk, just as they do on the continent.'
   'Try to keep your balance on the tightrope, as I do, by spreading out your fingers like this.'
   'The first ten days of July were very wet this year, as they were last year and the year before.'

In informal English, like is used in the same way. This is particularly common in American English. Consider the following:
   'Nobody else would look after you like I do, baby!'
   'She needs the money, like I do, so she works in a bar in the evenings.'
   'I hope you’re not going to be sick again, like you were when we went to Brighton.