Notes01 - CS 245: Database System Principles Notes 01:...

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1 CS 245: Database System Principles CS 245 Notes 1 1 Notes 01: Introduction Hector Garcia-Molina Isn’t Implementing a Database System Simple? Relations Statements Results CS 245 Notes 1 2 Introducing the Database Management System CS 245 Notes 1 3 • The latest from Megatron Labs • Incorporates latest relational technology • UNIX compatible Megatron 3000 Implementation Details First sign non-disclosure agreemen CS 245 Notes 1 4 First sign non disclosure agreement Megatron 3000 Implementation Details • Relations stored in files (ASCII) e.g., relation R is in /usr/db/R CS 245 Notes 1 5 Smith # 123 # CS Jones # 522 # EE . . . Megatron 3000 Implementation Details • Directory file (ASCII) in /usr/db/directory CS 245 Notes 1 6 R1 # A # INT # B # STR … R2 # C # STR # A # INT … . . .
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2 Megatron 3000 Sample Sessions % MEGATRON3000 Welcome to MEGATRON 3000! CS 245 Notes 1 7 % . . . Megatron 3000 Sample Sessions from R # CS 245 Notes 1 8 Relation R A B C SMITH 123 CS Megatron 3000 Sample Sessions from R,S where R A = S A and S C > 100 # CS 245 Notes 1 9 where R.A = S.A and S.C > 100 # A B 123 CAR 522 CAT Megatron 3000 Sample Sessions from R | LPR # CS 245 Notes 1 10 Result sent to LPR (printer). Megatron 3000 Sample Sessions from R where R A < 10 0|T# CS 245 Notes 1 11 where R.A < 100 | T # New relation T created. Megatron 3000 • To execute “ select * from R where condition ”: (1) Read dictionary to get R attributes (2) Read R file, for each line: (a) Check condition CS 245 Notes 1 (a) Check condition
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3 Megatron 3000 • To execute “ select * from R where condition | T ”: (1) Process select as before (2) Write results to new file T CS 245 Notes 1 13 (3) Append new line to dictionary Megatron 3000 • To execute “ select A,B from R,S where condition ”: (1) Read dictionary to get R,S attributes
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Notes01 - CS 245: Database System Principles Notes 01:...

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