The New Key/Index dialog allows you to select the type of Key/Index you wish to add.
ð Type
| Specifies the constraint type.
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| Primary Key
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| A column or set of columns that uniquely identify a row; in other words, each value in a primary key column is unique. A primary-key constraint prevents duplicate (non-unique) and null values from being entered. Even if you do not specifically define a constraint, all tables (in a well-designed database) should have a primary key. You can define one primary key per table.
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| Unique Key
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| A column or set of columns that uniquely identify a row; in other words, each value in a unique-key column is unique. A unique-key constraint prevents duplicate (non-unique) and null values from being entered. The only difference between a unique key and a primary key is that you can define multiple unique keys per table.
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| Index
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| A virtual record set to make data retrieval quicker.
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| When you apply an index to a column, R:BASE records the location of every value in that column. Then, when you look for or sort information in the column, R:BASE uses the index to find the rows you need quickly. For example, you want to list the bonuses that employee 102 earned; if the empid column in the salesbonus table is indexed, R:BASE finds and searches that column faster. Indexes are most useful when you have tables with many rows.
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| Foreign Key
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| A column or set of columns that match values in a particular primary key or unique key defined in a different table. A value cannot be inserted or changed.
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