GATE Overflow Test Series | Databases | Test 1 | Question: 12

Question

Consider the relations $R(A,B,C)$ and $S(B,C,D)$ and the following SQL queries.

1. Select distinct $\ast$ from $R,S;$
2. Select distinct $\ast$ from $R,S$ where $R.C = S.C;$
3. Select distinct $\ast$ from $R,S$ where $R.C = S.C$ and $R.B = S.B;$
4. Select distinct $\ast$ from $R,S$ where $R.C != S.C;$

Match the following Table where the first column refers to the four given SQL queries
$$
\begin{array}{|c|cl|}\hline
i. &a. & \text{Equi Join} \\
\hline
ii. &b.& \text{Natural Join}\\
\hline
iii. &c.& \text{Theta Join}\\
\hline
iv. &d.& \text{Cross Product}\\
\hline
\end{array}$$

• A. $i-d,ii-a,iii-c,iv-b$
• B. $i-b,ii-a,iii-d,iv-c$
• C. $i-d,ii-a,iii-b,iv-c$
• D. $i-c,ii-a,iii-b,iv-d$

Comments

Reference:https://stackoverflow.com/questions/7870155/difference-between-a-theta-join-equijoin-and-natural-join/7870216

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Sir i don’t think here any of the options are correct .

Moreover in option C which is given answer they are saying that query III is natural join which is not at all correct because the schema of the result obtained in query and schema of natural itself do not match.

Sir please look into this question @GO Classes.

Answer 1

option c)

Type of JOINS

Comments

Please send this link in command or inbox me bro

It is nice explanation