Computer Programming Concepts and Visual Basic David I. Schneider

338 Computer Programming Concepts and Visual Basic
COMMENTS
1. Each record of the Countries table is related to one or more records of the Cities
table, but each record of the Cities table is related to only one record of the
Countries table. Therefore, we say that there is a one-to-many relationship
from the Countries table to the Cities table.
2. SQL statements are insensitive to case. For instance, the following choices for
criteria have the same effect: City=‘China’, city=‘china’, CITY=‘china’,
CiTy=‘CHINA’.
3. When the Like operator is used, the “pattern” must appear on the right of the
operator. For instance, the SQL statement
SELECT * FROM Cities WHERE city Like ‘S*’
cannot be replaced by
SELECT * FROM Cities WHERE ‘S*’ Like city
4. The operator Like permits a refinement of the wildcard character “?”. Whereas
“?” is a placeholder for any letter, an expression such as “[letter1-letter2]” is a
placeholder for any letter from letter1 to letter2. For instance, the pattern “[A-
F]ad” is matched by Bad and Dad, but not Sad.
5. The Like operator can be used in If blocks in much the same way as the operators
>, =, and