Why is there a performance difference between two similar queries where one uses union and the other uses union all?

1028

---

What is a derived table?

923

---

Your sql server is running out of disk space. You notice that there are several large files with ldf extensions what are these files?

1182

---

Will the writetext statement activate a trigger?

1089

---

Other than truncate statement, which other command can by-pass the trigger on the tables?

1132

---

Is it important for a database administrator to understand the operating system and file access?

982

---

What is the fastest way to permanently delete a 1 million row table named customers?

1253

---

How do you rebuild an identity column?

946

---

Define a cross join?

1012

---

Explain an incremental backup?

998

---

How will you know when statistics on a table are obsolete?

1077

---

How you can find out if an index is useful to the optimizer?

937

---

You want to check the syntax of a complicated update sql statement without executing it. What command should you use?

983

---

What are statistics?

993

---

Can a unique index be created on a column, which contains null?

917

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