In a cached system, the base addresses of the last few referenced pages is maintained in registers called the TLB that aids in faster lookup. TLB contains those page-table entries that have been most recently used. Normally, each virtual memory reference causes 2 physical memory accesses-- one to fetch appropriate page-table entry, and one to fetch the desired data. Using TLB in-between, this is reduced to just one physical memory access in cases of TLB-hit.

mysql_fetch_array - Fetch a result row as an associative array and a numeric array.
mysql_fetch_object - Returns an object with properties that correspond to the fetched row and moves the internal data pointer ahead. Returns an object with properties that correspond to the fetched row, or FALSE if there are no more rows
mysql_fetch_row() - Fetches one row of data from the result associated with the specified result identifier. The row is returned as an array. Each result column is stored in an array offset, starting at offset 0.

mysql_fetch_array - Fetch a result row as an associative array, a numeric array, or both
mysql_fetch_assoc - Fetch a result row as an associative array

mysql_fetch_object - Fetch a result row as an object
mysql_fetch_row -- Get a result row as an enumerated array

MySQL fetch object will collect first single matching record where mysql_fetch_array will collect all matching records from the table in an array.

There are three types of buses. Address bus: This is used to carry the Address to the memory to fetch either Instruction or Data. Data bus : This is used to carry the Data from the memory. Control bus : This is used to carry the Control signals like RD/WR, Select etc.

Oracle Call Interface is a method of accesing database from a 3GL program. Uses-No precompiler is required,PL/SQL blocks are executed like other DML statements. The OCI library provides 1.functions to parse SQL statements 2.bind input variables 3.bind output variables 4.execute statements 5.fetch the results

It depends what the logic is. If you need to do complex manipulation of data already in the database, it is probably better than trying to run sql queries and fetch the data into the middle tie and perform the manipulation in the middle tie, then send the large amount of data back to the database using sql insert or update. On the other hand, you can do to something simple using sql, but you have to write quite a lot of code in stored procedure, why do that.

For stored procedure vs. dynamic sql queries, assuming you are not talking about case where you can call stored procedure within a sql query or you can use dynamic sql inside a stored procedure, dynamic query has a downside (at least in Oracle db), that it has to be compiled if the exact sql string is not used recently (seconds I think) by any session, which could takes some time, and use some system resource. On the other hand, logic in stored procedure is not necessary automatically better.

I think you have to compare approaches based on how easy it is to write the code to do what you want, how easy it is for others to understand and maintain the code, and what is the performance cost in a target database, etc.

The biggest disadvantage is that PS queries cannot be used to perform DML(update,insert,detele) operations. It can only fetch data(Select).

 If we use SQL directly then it will go to database directly to fetch rows of data. But if u write SQL'S in peoplecode, then the trip will be from application server to database because peoplecode resides in app server.
One should avoid writing SQL'S in App engine peoplecode as it would degrade the performance.