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Modifying Columns (Visual Database Tools)

  • Статья

To add, change, or delete columns in a table, use Table Designer. In Table Designer, each table column appears as a row in a grid, and the columns of the grid represent the properties of the table column.

To define a table's columns, edit the properties shown in the Column Properties tab in the lower pane of Table Designer. For details about the properties that are available in your database, see your database documentation.

Note

Changing table columns can cause code and applications that depend on the modified column to fail. These include queries, views, stored procedures, user-defined functions, and client applications. Note that these failures will cascade. For example, a stored procedure that calls a user-defined function that depends on the modified column may fail. Carefully consider any changes you want to make to a table column.

In This Section

  • How to: Specify Default Data Types for Columns
    Describes how to change the default data type for a column. The default data type is used when you create a new column in Table Designer without specifying a data type.

  • How to: Specify Default Values for Columns
    Describes how to set the default value for a column. The default value for a column is used when you add a new row to a table without specifying a column value.

  • How to: Specify Computed Columns
    Describes how to enter a computed column expression and set properties for the column and expression. Computed columns use a mathematical or other expression to generate results for a column, optionally using data from other columns.

  • How to: Modify Column Data Types
    Describes how to modify the data type of a column. A column's data type defines the type of data allowed in the column.

  • How to: Modify Column Length
    Describes how to modify the length of a column with a nonnumeric data type.

  • How to: Modify Column Precision
    Describes how to change the length, or precision, of a column with a numeric data type. The precision of a data type is the number of digits allowed in the column.

  • How to: Modify Column Scale
    Describes how to change the scale of a column with a numeric data type. The scale of a numeric data type is the number of digits to the right of the decimal point.

  • How to: Modify Column Identity Properties
    Describes how to change the identity properties of a column. Identity properties pertain to identity columns, which guarantee the uniqueness of the row to which the identity column belongs. Identity properties define, among other things, how new values are determined when a row is added.

  • How to: Modify Null Options on Columns
    Describes how to change the null options on columns.

  • Working with Columns
    Contains help about designing tables by adding and removing columns and changing column properties.