Temp table, table variable and table expression comparision...

Question: Could you please review this comparison table between temp tables, table variables, and table expressions? There are seven entries as listed. The items with ??? are missing where I need most help but it will nice to have your comment on others as well.Temps
a. Scope
a1. Temp tables are visible only to a session across all batches (if local) and visible across a session if global.
a2. Table variables are visible only to the batch that declared them and are destroyed at the end of the batch.
a3. N/A because table expressions do not have physical representation and their scope equates those of table called by such a table expression.

b. Can apply DDL after creation/declaration?
b1. Can apply a DDL to temp tables after it is created.
b2. ???
b3. n/a

c. Can have indexes?
c1. Can have indexes and other DDL changes.
c2. ???
c3. n/a

d. Affected by rollback/ logged?
d1. Yes.
d2. No.
d3. n/a

e. Has distribution statistics?
e1. Yes. Allows histogram.
e2. No.
e3. n/a

f. Has physical presence in temp db?
f1. Yes
f2. Yes
f3. No.

g. Suitable for what table size?
g1. Large data
g2. Small data
g3. ???

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LVL 34
Mike EghtebasDatabase and Application DeveloperAsked:
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ste5anSenior DeveloperCommented:
a1: Local temp tables are only visible in the session where created. Global temp tables are visible in all sessions.

b2, c2: It's a variable. DDL could not be applied.

g: You use what you gives the best performance.

The data size is only a criteria between temp table and table var, cause the optimizer uses an fixed value of 1 for the row estimate. This may lead to non optimal plans.
Whether you chose an temp table/variable or a CTE depends on whether a materialized intermediate result improves the query plan.

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