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It is not necessary to understand all the IMAGE features in
order to use QUERY. However, it is important to have a general idea
of data base structure and know the definitions of some IMAGE terms
which will be used in this manual.
Each item of information in a data base is referenced by a data item
name. The name associates the information with characteristics
which describe it:
the type of information (numeric, alphanumeric, etc.)
its relation to other data in the data base
the passwords required to read and/or write the
information
The data base designer organizes data items into data sets for the
purpose of accessing them as a group. For example, an employee data set could
contain the items EMPID, F-NAME, L-NAME, SOCSEC#, and
SALARY. A credit union data set could contain EMPID,
AMOUNT, TRANSCODE, and so forth. Each data set is referenced by
a data set name.
Each time you enter a new employee's record into the data
base, you can supply a value for each data item. This group of values
is stored as a single data entry in the data
set. For example:
F-NAME SALLY
L-NAME MERTON
SOCSEC# 527-58-6492
SALARY 18000.02
QUERY allows you to locate particular entries which have values
you specify. You can then change the values or print them in a report.
You can also add or delete an entire entry if your password gives
you the capability to write to each item in the data set.
You can use the FORM command to display the names of each data set to which you
have access and the names of the data items in those sets. Only the items to
which you have at least read access are listed.
If you are referring to a data item which appears in more
than one data set and/or data base, you must specify which data
set and data base to access. A particular data item can appear in
more than one data set within a given data base, and a particular
data item can appear in more than one data base. You can specify
the data item in three ways:
by specifying the data set through the DATA-SET= command and the
data base through the DBLIST= command.
by specifying the data set through the DEFINE command
(DATA-SETS= prompt) or through the MULTIDB command
(DATA-SETS= prompt).
by qualifying the data item name.
A fully-qualified data item name has the following form:
data base name:data set name.data item name
For example:
BADGE# is the name of a data item in the data set named LABOR
which is in a data base named IRONCO. If BADGE# is also the name
of a data item in a data set named EMPLOYEE, which is also in the
IRONCO data base, its fully-qualified name would be IRONCO:EMPLOYEE.BADGE#.
The data base designer defines each data item as a particular
type, depending on what kind of information is to be stored in the
item. A data item may be one of several types of integers, real
or floating-point numbers, or ASCII character information.
The FORM command can display the data type for each item.
When using QUERY, you will usually be unconcerned with the specific
data type with the following exceptions:
when supplying values for an item, either to enter new information
or to locate specific entries, you may want to know the acceptable
range of values for a numeric type item.
when creating reports you should be aware of the item types in
order to format the report properly.
when using the QUERY registers while printing a report, it is
helpful to know how calculations affect the register values.
Detailed information about each of these situations is given with the
appropriate command. Table 1-1 "Data Item Types
and Values" contains a summary of the data item types and the range of
acceptable values for each.
If you use QUERY to enter a value for a data item of type
P (packed decimal), you should be aware of the way QUERY handles
the sign of the value. A different code is used for the sign of
a value entered with a plus sign than for a value entered without
a sign. However, when QUERY retrieves unsigned and positive type
P data items with the same value, they are considered to be equivalent.
For example, +2 and 2 are equivalent. Data items with values +0,
0, and -0 are also equivalent.
If a character itme (x or u type) contains a binary zero value (null) in its
first character,m QUERY will report the value as 'NULL ITEM'.
Literals
When specifying the value of a particular data item, you must
sometimes surround the value with quotation marks. This type of
value is called a literal. A character or string literal contains
alphanumeric characters. For example:
"TANYA OAKLEY" "ZXR=93458273" "3215"
Character literals containing numeric values of the types listed under Integer
or Real in Table 1-1 "Data Item Types and
Values" are called, more specifically, numeric literals. For example:
"5468" "+408E-15" "-16.73892"
Rules for using quotation marks are described with the commands
which allow or require their use.
Table 1-1 Data Item Types and Values
TYPE |
MINIMUM |
MAXIMUM |
INTEGER |
I1 | -32768 | +32767 |
I2 | -2,147,483,648 | +2,147,483,647 |
I4 | -9,223,372,036,845,775,808 |
+9,223,372,036,854,775,807 |
J1 | -9999 | +9999 |
J2 | -999999999 | +999999999 |
J4 | -999999999999999999 |
+999999999999999999 |
K1 | 0 | +65535 |
K2 | 0 | +4,294,967,295 |
Zn * | - (n digit number) |
+ (n digit number) |
Pn * | - (n - 1 digit number) |
+ (n - 1 digit number) |
* n cannot exceed 255 and must be even for
type Z and evenly divisible by 4 for type Pn. QUERY reports
print at most 20 digits for type Z and 19 digits for type P data
values. |
REAL |
R2 | -1.157920 × 1077
-0.863617 × 10-77 | +0.863617 × 10-77
+1.157920 × 1077 |
Largest accurate absolute integer is 8,388,607.
(QUERY rounds to 6 digits when printing R2 values.) |
R4 | -1.157920892373161 × 1077
-0.8636168555094445 × 10-77 | +0.8636168555094445 × 10-77
+1.157920892373161 × 1077 |
Largest accurate absolute integer is 36,028,797,018,963,967.
(QUERY rounds to 16 digits when printing R4 values.) |
QUERY uses the R4 datatype for all REAL calculations and so
the limitations described above apply to E types |
E2 | -3.402823 x 1038
1.401298 x 10-45 | -1.401298 x 10-45
3.402823 x 1038 |
E4 | -1.797603134862315 x 10308
4.040656458412466 x 10-324 | -4.040656458412466 x 10-324
1.797603134862315 x 10308 |
CHARACTER |
Un ** | 1 ASCII character (lower case not allowed) |
n ASCII characters (lower case not allowed) |
Xn ** | 1 ASCII character |
n ASCII characters* |
** n cannot exceed 255. QUERY reports print at most 136
characters for type U and X data values.
IMAGE allows the data base designer to specify compound data
items. A compound data item is one that occurs more than once in
the same data entry. Each occurrence of the data item is called
a sub-item. Each sub-item can have a value, and QUERY can locate
and update any or all sub-items. If you update only the first sub-item,
QUERY preserves the existing values of all other sub-items.
There are three types of IMAGE data sets: manual
master, automatic master, and detail. Master
data sets are related to detail data sets through specific items
called search (or key) items. The FORM command identifies the data
set type and search items.
The data base designer can specify one or more sort items.
These items are also identified by the FORM command. As a QUERY
user, it is not necessary to understand the function of sort items.
If you want to know more about data set relations and sort items, refer to the
IMAGE Reference Manual description of the data base structure.
Figure 1-1 "ORDERS Data Base Structure" and
Figure 1-2 "Sample Entry Values" illustrate
a sample data base named ORDERS. The data base is used in many examples
in this manual. It contains six data sets. The four master data
sets are shown in the center column and the detail data sets on the sides.
CUSTOMER contains information about each customer.
SUP-MASTER contains information about each supplier.
PRODUCT contains information about each product.
DATE-MASTER is an index of dates and can be used to retrieve
information by date from the SALES or INVENTORY data sets.
SALES contains credit and purchase information.
INVENTORY contains product supply information.
Both figures show a single entry for each data set.
Figure 1-1 "ORDERS Data Base Structure"
contains the data item names, and Figure 1-2
"Sample Entry Values" contains a sample of the values in one entry. The
arrows in both figures illustrate the relationship of the data sets through
search items.
Note: This data base is not meant to be a practical application but rather is
designed to illustrate as many IMAGE/QUERY features as possible.
Figure 1-1 ORDERS Data Base Structure
Figure 1-2 Sample Entry Values
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