Pitney Bowes MapInfo Professional - Manual (Page 444)

Using Logical Operators in Expressions
"And", "or", and "not" are logical operators. You use them to combine expressions in Select and the
Where Condition clause of SQL Select. MapInfo Professional treats each such an expression as a test,
which it applies to each record in the table. For each test it gets a yes/no (true/false) answer. MapInfo
Professional uses the logical operators to tell it how to combine the individual yes/no answers into an
overall yes/no answer: Does the current record meet the selection condition?
Description Operator
is "true" if (and only if) both of its arguments (the expressions it joins
together) are true. A record must satisfy both of these conditions if
it is to be selected. and
is "true" if either one, or both, of its arguments (the expressions it
joins together) are true. A record need satisfy only one of these or
conditions if it is to be selected. It is also selected if both of its
conditions are satisfied.
is "true" if its argument (the expression it applies to) is false. A record
is selected if it does not meet the stated condition. not
Suppose you want to select all properties that are worth $250,000 or more and are in Columbia county.
Each record has to meet two criteria, each of which can be formulated as a simple expression:
1. VALUE >= 250000
2. COUNTY = "Columbia"
You could perform one selection for all properties worth $250,000 or more. Then you could perform
another selection on that result, looking for all properties in Columbia county. However, it is easier to
combine the two operations into one using the logical operator "and".
1. COUNTY = "Columbia" and VALUE >= 250000
When MapInfo Professional examines a record to see whether or not it meets the condition set by this
expression, it makes the two tests: Does COUNTY equal Columbia? Is the VALUE equal to or greater
than 250000? When the answer to both of these questions is true (or yes), then the record is accepted
into the current selection. When the answer to one or both of the questions is no (or false), then the
record is not accepted into the current selection.
Now, what if you want all properties worth $250,000 or more and not in Columbia county? You can use
"not" to negate the first clause of expression 33, yielding expression 34:
1. not (COUNTY="Columbia") and VALUE>=250000
Only records where the county is not Columbia satisfy the first clause of expression 34. Now consider
expression 35:
1. not (COUNTY="Columbia" and VALUE>=250000)
Expression 35 is simply the negation of expression 33. Any record that would satisfy 33 does not satisfy
35. Any record that does not satisfy 33 satisfies 35.
You can use "or" when you want to specify alternative conditions, such as:
1. COUNTY="Columbia" or COUNTY="Greene"
Any record evaluated against this condition is accepted if its county is any one of the two specified
counties. One could, of course, use numerical tests as well. For example:
1. TOTAL_AREA>40 or VALUE>250000
This tests to see whether the area is greater than 40 or the value is greater than 250000. When either
one is true of a record, then that record is accepted into the selection.
MapInfo Professional 12.5 444
Creating Expressions