Power-Programmierung/CD1.mdf/sql/create.shr

Text File | 1988-03-06 | 5KB | 177 lines

         CREATE A TABLE

         The create command is used to create a table file.

         SYNTAX
         CREATE TABLE table_name (
            column_name  data_type  column_width
           [column_name  data_type  column_width]
         ) number_of_rows;

         EXAMPLE:

         SSQL> create table cust (
             > code char 2
             > name char 15
             > st char 2
             > rating num 2
             > ) 20;

         The above definition was used to create the cust table used in the
         documentation.  You can define up to 32 columns in a table.
         Once a table is created, you can use the insert command to add
         rows to the table.

         table_name

         A table name can be from 1 to 8 characters.  The first character
         must be a letter of the alphabet.  The rest can be letters or
         digits.  The table file is created on the disk as
         table_name.SQL.  For example, the cust table, created above would
         be stored as CUST.SQL on your disk.  However, from SSQL, you would
         always refer to it as cust.  Since SSQL adds the extension of SQL
         to all table files, you must not use a period in your table
         name.

         column_name

         A column name can be from 1 to 10 characters.  The first
         character must be a letter of the alphabet.  The rest can be
         letters or digits.  In creating column names remember that when
         a table is displayed, the full column name is displayed too.
         Long column names tend to fill the screen (or printer) very
         rapidly when you want to display many columns.

         data_type and column_width

         NUMBERS

         The data type num is used for numbers.  When you use this data
         type the values are always right-justified (values are pushed to
         the right so all the ones column lines up).  Data must be of
         this type in order to use any of the numeric functions such as
         avg, max, min, and sum.




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         For the data type num, the column width can be from 1 to 10
         digits.  Optionally, you can add a decimal indicator for numeric
         functions.  For Example:
           cost  num  5.2
         This would allow a maximum of 99.99 to be stored in the column
         if you always used the decimals.  The ONLY time the number of
         decimal places is checked is when a numeric function takes
         place, NOT when you are entering data.  If you have a column
         which stores dollars and cents, remember to always enter the
         cents even if it is "00".  This would avoid the problem of
         entering 15 and 23.65 and have the column be displayed as:
              15
           23.65

         It is allowable to use whole numbers even though you define it
         as having decimals.  For example, you want to enter grades
         which are from  0 to 100 but when you calculate grade averages,
         you want it calculated to one tenth of a grade point.  You would
         define the column as:
           grade  num  3.1

         You would enter the grades as whole numbers but when the average
         is calculated, the decimal would be included.  The column width
         is increased by five when a numeric function is used.  This
         makes it possible to define something like:
           level  num  2.4
         You could only enter 1-99, but when the average was calculated,
         it would be to four decimal places.

         CHARACTERS

         The data type char can be used for any column that is not used
         in a calculation.  Although the data is usually a combination of
         alphabetic and numeric data, it is alright if the column just
         contains digits.  The characters are left-justified.  The
         maximum column width is 80.

         number_of_rows

         The last item you enter is the maximum number of rows that you
         want in the table.  The minimum number of rows is 11.  If you
         enter a number less than 11, the table will be created with 11
         rows.  The maximum number allowable is 32000.






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         DETERMINING HOW A TABLE WAS CREATED (The STRUCT command)

         In order to display the create command used to create the table,
         type:

         STRUCT table_name;

         where table_name is the name of a table that exists in you
         database.  For example, to display the table structure for the
         cust table you would type:

         struct cust;







































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