Module 13 (Introduction to SQL - Part 2).pdf

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The OUTER JOINAs a matter of good database designpractice, you should avoid outer joins asmuch as possible, because of the addedcomplexity and extra code needed to handlethe resulting special cases.Try instead to use left joins consistently,always expressing the query so that theselection of the left-hand table makes sense.
The CROSS JOINThis is a very odd type of join. In a cross join,every record from the left-hand table is matched toevery record from the right-hand table, in amultiplicative way. The resulting recordset can behuge (that is, m × n records).Thus, if we had 500 employees and 40000 ordersin our database (and didn’t use any WHERE clauseto limit our selection), a CROSS JOIN wouldreturn 500 x 40000 = 20,000,000 records!
Page 1 and 2:
Whirlwind Tour of SQL, Part 2Web an
Page 3 and 4: AGGREGATE FUNCTIONS
Page 5 and 6: Aggregate FunctionsConsider this co
Page 7 and 8: Aggregate FunctionsSince the name w
Page 9 and 10: Aggregate FunctionsIn general, you
Page 11 and 12: Aggregate FunctionsFunction UseAppl
Page 13 and 14: Aggregate FunctionsIf all we could
Page 15 and 16: Aggregate FunctionsYou do not have
Page 17 and 18: GroupingIn the first query, the sum
Page 19 and 20: GroupingIncidentally, the above is
Page 21 and 22: JOIN CLAUSES
Page 23 and 24: The JOIN ClauseJoins usually make u
Page 25 and 26: Design StrategiesThis is generally
Page 27 and 28: The JOIN ClauseThe join key or comm
Page 29 and 30: The JOIN ClauseThe above query will
Page 31 and 32: Speeding Things UpWe could have wri
Page 33 and 34: Relationships among TablesThe way w
Page 35 and 36: One-To-ManyOne-to-Many: The most li
Page 37 and 38: Showing RelationshipsIn the query w
Page 39 and 40: Showing RelationshipsNotice this re
Page 41 and 42: TYPES OF JOIN CLAUSES
Page 43 and 44: The INNER JOINThis is the default t
Page 45 and 46: The INNER JOINIn the above example,
Page 47 and 48: The LEFT JOINThe LEFT JOIN specifie
Page 49 and 50: The RIGHT JOINThe RIGHT JOIN specif
Page 51 and 52: The OUTER JOINThe OUTER or FULL JOI
Page 53: The OUTER JOINThis means possibly g
Page 57 and 58: The CROSS JOINHowever, when running
Page 59 and 60: Using JOIN and WHEREOf course, we c
Page 61 and 62: Using JOIN and ORDER BYWe can also
Page 63 and 64: Using JOIN and WHEREHere, the sort
Page 65 and 66: Compound JoinsFinal ResultsResults
Page 67 and 68: Compound JoinsThis example produces
Page 69 and 70: Compound JoinsThe Sum(Ccur(...)) po
Page 71 and 72: Compound JOINsIn the JOIN section,
Page 73 and 74: The Self JOINThis is used to join a
Page 75 and 76: Non-Equi JOINsBut this will give us
Page 77 and 78: SubqueriesThis is a powerful techni
Page 79 and 80: SubqueriesThis example involves usi
Page 81 and 82: SubqueriesThe third example, involv
Page 83 and 84: SELECT … INTO StatementsEverythin
Page 85 and 86: SELECT … INTO StatementsThe list
Page 87 and 88: INSERT STATEMENTS
Page 89 and 90: The INSERT VerbThe easiest way to a
Page 91 and 92: The INSERT VerbWhere:• tablename
Page 93 and 94: INSERT ExampleEvery value given in
Page 95 and 96: INSERT ExampleAlso note that we nei
Page 97 and 98: The INSERT VerbBecause it is so use
Page 99 and 100: A Better ApproachOr… put the code
Page 101 and 102: Notes About INSERTThere are usually
Page 103 and 104: Notes about INSERTDEFAULT can be us
Page 105 and 106:
The DELETE VerbThe DELETE verb is a
Page 107 and 108:
The DELETE VerbHere is one that mig
Page 109 and 110:
The DELETE VerbOften, you should gi
Page 111 and 112:
The UPDATE VerbThe UPDATE command a
Page 113 and 114:
UPDATE ExampleThis one might make m
Page 115 and 116:
UPDATE ExampleOf course this might
Page 117 and 118:
SQL TransactionsA critically import
Page 119 and 120:
SQL TransactionsIt would be disastr
Page 121 and 122:
SQL TransactionsIn SQL, it might lo
Page 123 and 124:
SQL TransactionsThe opposite of a C
Page 125 and 126:
CONCLUSIONS
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