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

989

---

What is a derived table?

874

---

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

1129

---

Will the writetext statement activate a trigger?

1003

---

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

1071

---

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

931

---

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

1159

---

How do you rebuild an identity column?

899

---

Define a cross join?

956

---

Explain an incremental backup?

942

---

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

1034

---

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

874

---

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

913

---

What are statistics?

955

---

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

882

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