wird ... schlecht

Question

The Cambridge dictionary has the following sentence. What is the subject of the following sentence? Is it an omitted "es"?

Da wird einem ja schon beim Zusehen schlecht!

Answer 1

The subject of a sentence can be a noun (more often a nominal groups who's core is a noun) or a pronoun.

• noun

  Käse stinkt.

• nominal group (with a noun as it's core)

  Der alte Mann schläft.

• pronoun

  Er schläft.
  Es regnet.

In sentences in active voice, the subject usually indicates the agent of the action, i.e. the person or thing that is doing something. But sentences like »Es regnet« show, that there are exceptions. The word es in this sentence is an expletive pronoun, that is the grammatically subject (because it's in nominative case¹), but it's not the agent, although the sentence is in active voice.

But there are also exceptions from the rule subject = agent that work the opposite way:

Mich friert.
Mir wird schlecht.
Vom Kuchen ist noch genug da.

The parts of speech that are marked bold here are the agents of their sentences, but they are not the grammatical subjects because they are not in nominative case. They are objects (accusative, dative and prepositional objects in this order).

This kind of exceptions works only with a small number of verbs and specific constructions. The combination werden + schlecht is such an example:

Mir wird schlecht. = I'm going to feel sick/nausea.
Ich werde schlecht. = I'm getting bad/evil.

Your sentence is a variation of »Mir wird schlecht«: Instead of the personal pronoun mir you can use a generalizing pronoun. In nominative case this would be man (»Man soll mehr trinken.«), but in dative case it is einem instead (»Das raubt einem den Verstand«). So, the generalized version of »Mir wird schlecht« is this:

Einem wird schlecht.
One is going to feel sick/nausea.

But this three words alone feel a little bit naked, so you can add a modal pronoun at position 1. But the verb must stay at position 2, so the word einem has to move to position 3:

Da wird einem schlecht.
In this case one is going to feel sick/nausea.

And then you can add even more stuff (What makes you feel sick?):

Da wird einem beim Zusehen schlecht.
In this case one is going to feel sick/nausea from watching.

And with some syntactical sugar (a modal particle and an adverb in this case) you get a really fine German sentence:

Da wird einem ja schon beim Zusehen schlecht!
literally: In this case one is going to feel sick/nausea already from watching!
free: It makes you sick just watching it!

_{Note: It makes you sick = Das macht einen krank. (krank = you have fever and have to stay in bed) But: Da wird einem schlecht = It makes you feel as if you soon have to vomit.}

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Just for completeness: Sometimes even a whole clause can be the subject of a German sentence:

Dass du das machst, ärgert mich.
The fact that you do this annoys me.

But that's another topic and far beyond the scope of your question.

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¹ _{In some sentences you have two parts in nominative case (»Georg ist Tischler«), but then only one of them is the subject, although sometimes it can be ambiguous which of them. (»Marillen sind Aprikosen«)}