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187 lines
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ReStructuredText
187 lines
15 KiB
ReStructuredText
.. _query_tool:
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**************
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The Query tool
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**************
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The Query tool is a powerful, feature-rich environment that allows you to execute arbitrary SQL commands and review the result set. If you access the Query tool via the *Query Tool* menu option on the *Tools* menu, you can:
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* Issue ad-hoc SQL queries.
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* Execute arbitrary SQL commands.
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* Save the data displayed in the output panel to a CSV file.
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* Review the execution plan of a SQL statement in either a text or a graphical format.
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* View analytical information about a SQL statement.
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If you open the Query tool via the *View Data* context-menu, the Query tool acts as a data editor, allowing you to:
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* View or modify the data that is stored in a table.
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* Filter the result set.
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* Save the data displayed in the output panel to a CSV file.
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* Review the execution plan of a SQL statement in either a text or a graphical format.
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* View analytical information about a SQL statement.
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.. image:: images/query_tool.png
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The Query tool features a toolbar that allows quick access to frequently used options, and a work environment divided into two panels:
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* The upper panel of the Query tool contains the *SQL Editor*. You can use the panel to manually enter a query, or review the query that generated the result set displayed in the lower panel.
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* The lower panel of the Query tool contains the *Data Output* panel. The output panel displays the result of a query, or information about a query's execution plan.
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pgAdmin allows you to open multiple copies of the Query tool (in individual tabs) simultaneously. For example, if you select *Query tool* from the *Tools* menu, the Query tool opens in a tab labeled *Query-1*; if you open the Query tool again (without closing *Query-1*), a second copy will open in *Query-2*. To close a copy of the Query tool, click the *X* in the upper-right hand corner of the tab bar.
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**The Query tool Toolbar**
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The *Query tool* toolbar uses context-sensitive icons that provide shortcuts to frequently performed tasks. If an icon is highlighted, the option is enabled; if the icon is grayed-out, the task is disabled.
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.. image:: images/query_toolbar.png
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Hover over an icon to display a tooltip that describes the icon's functionality:
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+----------------------+---------------------------------------------------------------------------------------------------+
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| Icon | Behavior |
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+======================+===================================================================================================+
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| *Open File* | Click the *Open File* icon to display a previously saved query in the SQL Editor. |
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+----------------------+---------------------------------------------------------------------------------------------------+
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| *Save* | Click the *Save* icon to save the query that is currently displayed in the SQL Editor. |
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+----------------------+---------------------------------------------------------------------------------------------------+
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| *Copy* | Click the *Copy* icon to copy the currently selected row. |
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+----------------------+---------------------------------------------------------------------------------------------------+
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| *Paste* | Click the *Paste* icon to paste the content that is currently on the clipboard. |
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+----------------------+---------------------------------------------------------------------------------------------------+
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| *Add New Row* | Use the *Add New Row* icon to add a new row in the output panel. |
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+----------------------+---------------------------------------------------------------------------------------------------+
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| *Filter* | Click the *Filter* icon to open a dialog that allows you to write and apply a filter for the |
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| | content currently displayed in the output panel. Click the down arrow to open the *Filter* drop- |
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| | down menu and select from pre-defined options: |
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| | |
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| | Select *Remove* to remove the currently applied filter and display the complete result set. |
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| | |
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| | Select *By selection* to refresh the displayed data, displaying only those rows that have columns|
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| | that match the currently highlighted value. |
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| | |
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| | Select *Exclude selection* to refresh the displayed data, excluding those rows that have columns |
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| | that match the currently highlighted value. |
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+----------------------+---------------------------------------------------------------------------------------------------+
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| *No limit* | Use the *No limit* drop-down listbox to specify how many rows to display in the output panel. |
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| | Select from: *No limit* (the default), *1000 rows*, *500 rows*, or *100 rows*. |
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+----------------------+---------------------------------------------------------------------------------------------------+
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| *Execute/Refresh* | Click the *Execute/Refresh* icon to either execute or refresh the query highlighted in the SQL |
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| | editor panel. Click the down arrow to access other execution options: |
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| | Select *Execute/Refresh* to invoke the SQL command and refresh the result set. |
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| | Select *Explain* to view an explanation plan for the current query. The result of the |
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| | EXPLAIN is displayed graphically on the *Explain* tab of the output panel, and in text |
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| | form on the *Data Output* tab. |
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| | |
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| | Select *Explain analyze* to invoke an EXPLAIN ANALYZE command on the current query. |
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| | Navigate through the *Explain Options* menu to select options for the EXPLAIN command: |
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| | Select *Verbose* to display additional information regarding the query plan. |
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| | Select *Costs* to include information on the estimated startup and total cost of each |
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| | plan node, as well as the estimated number of rows and the estimated width of each |
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| | row. |
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| | Select *Buffers* to include information on buffer usage. |
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| | Select *Timing* to include information about the startup time and the amount of time |
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| | spent in each node of the query. |
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| | |
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| | Add a check next to *Auto-Rollback* to instruct the server to automatically roll back a |
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| | transaction if an error occurs during the transaction. |
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| | Add a check next to *Auto-Commit* to instruct the server to automatically commit each |
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| | transaction. Any changes made by the transaction will be visible to others, and |
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| | durable in the event of a crash. |
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+----------------------+---------------------------------------------------------------------------------------------------+
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| *Stop* | Click the *Stop* icon to cancel the execution of the currently running query. |
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+----------------------+---------------------------------------------------------------------------------------------------+
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| *Clear query window* | Use options on the *Clear query window* drop-down menu to erase the contents of |
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| | the SQL editor panel or the *History* tab. |
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+----------------------+---------------------------------------------------------------------------------------------------+
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| *Download as CSV* | Click the *Download as CSV* icon to download the result set of the current query to a |
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| | comma-separated list. |
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+----------------------+---------------------------------------------------------------------------------------------------+
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**The SQL Editor Panel**
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The *SQL editor* panel contains a workspace for entering commands; you can read a query from a file, or type a query. The SQL editor features syntax coloring and autocompletion to help you develop queries.
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.. image:: images/query_sql_editor.png
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To use autocomplete, begin typing your query; when you would like the Query editor to suggest object names or commands that might be next in your query, press the Control+Space key combination. For example, type "\*SELECT \* FROM\* " (without quotes, but with a trailing space), and then press the Control+Space key combination to select from a popup menu of autocomplete options.
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.. image:: images/query_autocomplete.png
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After entering a query, select the *Execute/Refresh* icon from the toolbar. The complete contents of the SQL editor panel will be sent to the database server for execution. To execute only a section of the code that is displayed in the SQL editor, highlight the text that you want the server to execute, and click the *Execute/Refresh* icon:
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.. image:: images/query_execute_section.png
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The message returned by the server when a command executes is displayed on the *Messages* tab of the output panel. If the command is successful, the *Messages* tab displays execution details:
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.. image:: images/query_tool_message.png
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The editor also offers several features that help with code formatting:
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* The auto-indent feature will automatically indent text to the same depth as the previous line when you press the Return key.
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* Block indent text by selecting two or more lines and pressing the Tab key.
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* Block outdent text that has been indented using the Shift+Tab key combination.
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* Comment out SQL by selecting some text and pressing Control+K.
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* Uncomment SQL by selecting some text starting with a comment and pressing Control+Shift+K.
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* Shift the selected text to upper case by pressing Control+U.
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* Shift the selected text to lower case by pressing Control+Shift+U.
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**The Data Output Panel**
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Use the *Data Output* panel of the *Query tool* to view data and information generated by a query in the *SQL editor*, or to *View Data* for an object currently selected in the *pgAdmin* tree control.
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The *Data Output* panel organizes output through the following tabs: *Data Output*, *Explain*, *Messages*, and *History*.
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.. image:: images/query_output_data.png
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If the Query tool is opened through the *Query tool* menu option on the *Tools* menu, you can use the *Data Output* tab to view the results of an arbitrary query in a table format. If the Query tool is opened through a *View Data* context menu, the *Data Output* tab will display the data stored in the table from which the Query tool was opened.
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* Click a column header to sort data by that column. Click again to reverse the sorting order.
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* If enabled, use the *Filter* options from the Query tool toolbar to refine the result set displayed on the *Data Output* tab.
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* If enabled, use the *No limit* drop-down to specify how many rows to display on the *Data Output* tab.
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* If enabled, use the *Execute/Refresh* options to retrieve query execution information and set query execution options.
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* Use the *Download as CSV* icon to download the content of the *Data Output* tab as a comma-delimited file.
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All rowsets from previous queries or commands that are displayed in the *Data Output* panel will be discarded when you invoke another query; open another query tool browser tab to keep your previous results available.
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Use the *Explain* tab to view a graphical representation of a query:
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.. image:: images/query_output_explain.png
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To generate a graphical explain diagram, open the *Explain* tab, and select *Explain*, *Explain Analyze*, or one or more options from the *Explain options* menu on the *Execute/Refresh* drop-down. Please note that *EXPLAIN VERBOSE* cannot be displayed graphically. Hover over an icon on the *Explain* tab to review information about that item; a popup window will display information about the selected object:
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.. image:: images/query_output_explain_details.png
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Note that the query plan that accompanies the *Explain analyze* is available on the *Data Output* tab.
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Use the *Messages* tab to view information about the last-executed query:
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.. image:: images/query_output_error.png
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If the server returns an error, the error message will be displayed on the *Messages* tab, and the syntax that cause the error will be underlined in the SQL editor.
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If a query succeeds, the *Messages* tab displays how long the query took to complete and how many rows were retrieved:
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.. image:: images/query_output_messages.png
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Use the *History* tab to review activity for the current session:
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.. image:: images/query_output_history.png
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The History tab displays:
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* The date and time that a query was invoked.
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* The text of the query.
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* The number of rows returned by the query.
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* The amount of time it took the server to process the query and return a result set.
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* Messages returned by the server (not noted on the *Messages* tab).
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To erase the content of the *History* tab, select *Clear history* from the *Clear query window* drop-down menu. |