mirror of
https://github.com/pgadmin-org/pgadmin4.git
synced 2024-12-24 08:00:09 -06:00
173 lines
7.0 KiB
ReStructuredText
173 lines
7.0 KiB
ReStructuredText
.. _column_dialog:
|
|
|
|
**********************
|
|
`Column Dialog`:index:
|
|
**********************
|
|
|
|
Use the *Column* dialog to add a column to an existing table or modify a column
|
|
definition.
|
|
|
|
The *Column* dialog organizes the development of a column through the following
|
|
dialog tabs: *General*, *Definition*, and *Security*. The *SQL* tab displays the
|
|
SQL code generated by dialog selections.
|
|
|
|
.. image:: images/column_general.png
|
|
:alt: Column dialog general tab
|
|
:align: center
|
|
|
|
Use the fields in the *General* tab to identify the column:
|
|
|
|
* Use the *Name* field to add a descriptive name for the column. The name will
|
|
be displayed in the *pgAdmin* tree control. This field is required.
|
|
* Store notes about the column in the *Comment* field.
|
|
|
|
Click the *Definition* tab to continue.
|
|
|
|
.. image:: images/column_definition.png
|
|
:alt: Column dialog definition tab
|
|
:align: center
|
|
|
|
Use the fields in the *Definition* tab to add parameters for the column. (Fields
|
|
are disabled if inapplicable.)
|
|
|
|
* Use the drop-down listbox next to *Data Type* to select a data type for the
|
|
column. For more information on the data types that are supported by
|
|
PostgreSQL, refer to Chapter 8 of the Postgres core documentation. This field
|
|
is required.
|
|
* Use the *Length/Precision* and *Scale* fields to specify the maximum number of
|
|
significant digits in a numeric value, or the maximum number of characters in
|
|
a text value.
|
|
* Use the drop-down listbox next to *Collation* to apply a collation setting to
|
|
the column.
|
|
|
|
Click the *Constraints* tab to continue.
|
|
|
|
.. image:: images/column_constraints.png
|
|
:alt: Column dialog constraints tab
|
|
:align: center
|
|
|
|
Use the fields in the *Constraints* tab to specify constraints for the column.
|
|
(Fields are disabled if inapplicable.)
|
|
|
|
* Use the *Default Value* field to specify a default data value.
|
|
* Move the *Not Null* switch to the *Yes* position to specify the column may not
|
|
contain null values. The default is *No*.
|
|
* Use the *Type* field to specify the column type (NONE/IDENTITY/GENERATED).
|
|
The default is *NONE*.
|
|
|
|
Click the *IDENTITY* type to create Identity column.
|
|
|
|
.. image:: images/column_constraint_identity.png
|
|
:alt: Column dialog constraints tab
|
|
:align: center
|
|
|
|
Use the following fields to create *IDENTITY* column. Identity columns are
|
|
applicable for PG/EPAS version 10 and above.
|
|
|
|
* Use the *Identity* field to specify ALWAYS or BY DEFAULT. This clause is
|
|
used to determine how the sequence value is given precedence over a
|
|
user-specified value in an INSERT statement.
|
|
* Use the *Increment* field to specify which value is added to the current
|
|
sequence value to create a new value.
|
|
* Provide a value in the *Start* field to specify the beginning value of the
|
|
sequence. The default starting value is MINVALUE for ascending sequences and
|
|
MAXVALUE for descending ones.
|
|
* Provide a value in the *Minimum* field to specify the minimum value a sequence
|
|
can generate. If this clause is not supplied or NO MINVALUE is specified,
|
|
then defaults will be used. The defaults are 1 and -263-1 for ascending and
|
|
descending sequences, respectively.
|
|
* Provide a value in the *Maximum* field to specify the maximum value for the
|
|
sequence. If this clause is not supplied or NO MAXVALUE is specified, then
|
|
default values will be used. The defaults are 263-1 and -1 for ascending and
|
|
descending sequences, respectively.
|
|
* Provide a value in the *Cache* field to specify how many sequence numbers are
|
|
to be preallocated and stored in memory for faster access. The minimum value
|
|
is 1 (only one value can be generated at a time, i.e., no cache), and this is
|
|
also the default.
|
|
* Move the *Cycled* switch to the *Yes* position to allow the sequence to wrap
|
|
around when the MAXVALUE or the MINVALUE has been reached by an ascending or
|
|
descending sequence respectively. If the limit is reached, the next number
|
|
generated will be the MINVALUE or MAXVALUE, respectively. The default is *No*.
|
|
|
|
Click the *GENERATED* type to create Generated column.
|
|
|
|
.. image:: images/column_constraint_generated.png
|
|
:alt: Column dialog constraints tab
|
|
:align: center
|
|
|
|
Use the following fields to create *GENERATED* column. Generated columns are
|
|
applicable for PG/EPAS version 12 and above.
|
|
|
|
* Use the *Expression* field to specify the generation expression. It can
|
|
refer to other columns in the table, but not other generated columns.
|
|
Any functions and operators used must be immutable. References to other
|
|
tables are not allowed.
|
|
|
|
Click the *Variables* tab to continue.
|
|
|
|
.. image:: images/column_variables.png
|
|
:alt: Column dialog variables tab
|
|
:align: center
|
|
|
|
Use the *Variables* tab to specify the number of distinct values that may be
|
|
present in the column; this value overrides estimates made by the ANALYZE
|
|
command. Click the *Add* icon (+) to add a *Name*/*Value* pair:
|
|
|
|
* Select the name of the variable from the drop-down listbox in the *Name* field.
|
|
|
|
* Select *n_distinct* to specify the number of distinct values for the column.
|
|
* Select *n_distinct_inherited* to specify the number of distinct values
|
|
for the table and its children.
|
|
|
|
* Specify the number of distinct values in the *Value* field. For more
|
|
information, see the documentation for
|
|
`ALTER TABLE <https://www.postgresql.org/docs/current/sql-altertable.html>`_.
|
|
|
|
Click the *Add* icon (+) to specify each additional *Name*/*Value* pair; to
|
|
discard a variable, click the trash icon to the left of the row and confirm
|
|
deletion in the *Delete Row* popup.
|
|
|
|
Click the *Security* tab to continue.
|
|
|
|
.. image:: images/column_security.png
|
|
:alt: Column dialog security tab
|
|
:align: center
|
|
|
|
Use the *Security* tab to assign attributes and define security labels. Click
|
|
the *Add* icon (+) to add each security label selection:
|
|
|
|
* Specify a security label provider in the *Provider* field. The named provider
|
|
must be loaded and must consent to the proposed labeling operation.
|
|
* Specify a a security label in the *Security Label* field. The meaning of a
|
|
given label is at the discretion of the label provider. PostgreSQL places no
|
|
restrictions on whether or how a label provider must interpret security
|
|
labels; it merely provides a mechanism for storing them.
|
|
|
|
Click the *Add* icon (+) to assign additional security labels; to discard a
|
|
security label, click the trash icon to the left of the row and confirm deletion
|
|
in the *Delete Row* popup.
|
|
|
|
Click the *SQL* tab to continue.
|
|
|
|
Your entries in the *Column* dialog generate a SQL command (see an example
|
|
below). Use the *SQL* tab for review; revisit or switch tabs to make any changes
|
|
to the SQL command.
|
|
|
|
Example
|
|
*******
|
|
|
|
The following is an example of the sql command generated by user selections in
|
|
the *Column* dialog:
|
|
|
|
.. image:: images/column_sql.png
|
|
:alt: Column dialog sql tab
|
|
:align: center
|
|
|
|
The example shown demonstrates creating a column named *sal* in the table
|
|
named *jobhist*.
|
|
|
|
* Click the *Info* button (i) to access online help.
|
|
* Click the *Save* button to save work.
|
|
* Click the *Close* button to exit without saving work.
|
|
* Click the *Reset* button to restore configuration parameters.
|