Added SQLExample

AppExamples/misc/SQLExample/doc/Documentation.md

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+# SQLExample
+
+![SQL Example Figure](sql_example.png)
+
+## Short description
+
+This example demonstrates how to access an SQL database from an App. For demonstration purposes, project keywords are written to or read from a database, respectively.
+
+The database access is implemented using [mysql-connector-python](https://pypi.org/project/mysql-connector-python/). A test database server is set up using [MySQL Community Server](https://dev.mysql.com/downloads/mysql/).
+
+Besides, <a href="../../python_api/python_api.html#gom-api-settings">gom.api.settings</a> is used to save and restore entries made in a dialog.
+
+## Highlights
+
+![SQL Example Dialog](sql_example_dialog_annotated.png)
+
+### 1. Accessing project keywords
+
+A project must be loaded to access project keywords. This is checked with the following code:
+
+```{code-block} python
+if not hasattr(gom.app, 'project'):
+  gom.script.sys.execute_user_defined_dialog (file='no_project.gdlg')
+  quit(0)
+```
+
+This App handles the project variables `user_project`, `user_company`, `user_department` and `user_part`.
+For each of these variables, two text widgets are used - one for the value in ZEISS INSPECT (e.g. `project_zi`) and one for the value in the database (e.g. `project_db`). 
+
+If available, the project keywords are written to the text widgets in the column 'INSPECT' (`*_zi`):
+
+```{code-block} python
+if 'user_project' in gom.app.project.project_keywords:
+  DIALOG.project_zi.value = getattr(gom.app.project, 'user_project')
+```
+
+The text widget entries in the column 'INSPECT' can be edited or loaded from the database (the database entry is selected by 'Project').
+
+Finally the project keywords are updated from the text widgets, if the dialog is closed with the 'Ok' button:
+
+```{code-block} python
+try:
+  RESULT = gom.script.sys.show_user_defined_dialog (dialog=DIALOG)
+except gom.BreakError as e:
+  # Dialog window was closed or 'Cancel' button was pressed
+  pass
+else:
+  # 'Ok' button was pressed
+  gom.script.sys.set_project_keywords (keywords = {
+    'project': RESULT.project_zi,
+    'company': RESULT.company_zi,
+    'department':  RESULT.department_zi,
+    'part': RESULT.part_zi
+  })
+```
+
+### 2. Installing a test database server
+
+Install the [MySQL Community Server](https://dev.mysql.com/downloads/mysql/) as shown in [Install MySQL Community Server on Windows](https://www.youtube.com/watch?v=2HQC94la6go).
+
+### 3. Accessing the database
+
+After the database server has been installed and started, you can try to connect to it, but the 'Connection Status' will show 'Unknown database "\<name\>"', because no database has been created yet.
+
+#### Creating a database
+
+A new database is created using the function `create_database()`, which calls [MySQLConnection.connect()](https://dev.mysql.com/doc/connector-python/en/connector-python-api-mysqlconnection-connect.html).
+
+1. A connection is established without specifying a database
+
+```{code-block} python
+def create_database(host_name, user_name, user_password, database):
+  try:
+	  connection = mysql.connector.connect(
+      host=host_name,
+      user=user_name,
+      passwd=user_password
+  )
+  except Error as err:
+    print(f"Error: '{err}'")
+    return err
+```
+
+2. The database is created
+
+The SQL command `CREATE DATABASE {database} DEFAULT CHARACTER SET 'utf8'` is passed as a parameter to the [MySQLCursor.execute()](https://dev.mysql.com/doc/connector-python/en/connector-python-api-mysqlcursor-execute.html) method.
+
+```{code-block} python
+cursor = connection.cursor()
+try:
+  cursor.execute("CREATE DATABASE {} DEFAULT CHARACTER SET 'utf8'".format(database))
+except mysql.connector.Error as err:
+  print(f"Failed creating database: {err}")
+  #return err
+else:
+  print(f"Created database {database}")
+```
+
+3. The database is selected
+
+Again, the method [MySQLCursor.execute()](https://dev.mysql.com/doc/connector-python/en/connector-python-api-mysqlcursor-execute.html) is called &mdash; this time with the SQL command `USE {database}`.
+
+```{code-block} python
+try:
+  cursor.execute("USE {}".format(database))
+except mysql.connector.Error as err:
+  print(f"Database {database} does not exists.")
+  print(err)
+else:
+  print(f"Using database {database}")
+```
+
+4. A database table is created
+
+Table: `projects`
+
+| project_no                      | project_name (unique)       | company_name         | department_name | part_name            |
+| ------------------------------- | --------------------------- | -------------------- | --------------- | -------------------- |
+| int(11) NOT NULL AUTO_INCREMENT | varchar(80) NOT NULL UNIQUE | varchar(80) NOT NULL | varchar(80)     | varchar(80) NOT NULL |  
+
+```{code-block} python
+# Database - projects table
+TABLES = {}
+TABLES['projects'] = (
+	"CREATE TABLE `projects` ("
+	"  `project_no` int(11) NOT NULL AUTO_INCREMENT,"
+	"  `project_name` varchar(80) NOT NULL UNIQUE,"
+	"  `company_name` varchar(80) NOT NULL,"
+	"  `department_name` varchar(80),"
+	"  `part_name` varchar(80) NOT NULL,"
+	"  PRIMARY KEY (`project_no`)"
+	") ENGINE=InnoDB")
+```
+
+The table data structure is passed as the SQL command to the method [MySQLCursor.execute()](https://dev.mysql.com/doc/connector-python/en/connector-python-api-mysqlcursor-execute.html).
+
+```{code-block} python
+for table_name in TABLES:
+  table_description = TABLES[table_name]
+  try:
+    print("Creating table {}: ".format(table_name), end='')
+    cursor.execute(table_description)
+  except mysql.connector.Error as err:
+    if err.errno == errorcode.ER_TABLE_EXISTS_ERROR:
+      print("already exists.")
+    else:
+      print(err.msg)
+      return err
+  else:
+    print("OK")
+```
+
+5. Final steps
+
+The methods [MySQLCursor.close()](https://dev.mysql.com/doc/connector-python/en/connector-python-api-mysqlcursor-close.html) and [MySQLConnection.close()](https://dev.mysql.com/doc/connector-python/en/connector-python-api-mysqlconnection-close.html) are called.
+
+```{code-block} python
+cursor.close()
+connection.close()
+return None
+```
+
+#### Connecting the database
+
+The function `create_server_connection()` creates a connection to the server and selects the database by calling [MySQLConnection.connect()](https://dev.mysql.com/doc/connector-python/en/connector-python-api-mysqlconnection-connect.html).
+
+```{code-block} python
+def create_server_connection(host_name, user_name, user_password, database):
+  connection = None
+  error = None
+  try:
+    connection = mysql.connector.connect(
+      host=host_name,
+      user=user_name,
+      passwd=user_password,
+      database=database
+    )
+    print("MySQL Database connection successful")
+  except Error as err:
+    print(f"Error: '{err}'")
+    error = err
+
+  return connection, error
+```
+
+#### Querying the database
+
+In this example, whe only use the project name for selecting database entries. The project names must be unique, so we use [MySQLCursor.fetchone()](https://dev.mysql.com/doc/connector-python/en/connector-python-api-mysqlcursor-fetchone.html) to get a single row from the `projects` table as result.
+
+```{code-block} python
+query = """SELECT company_name, department_name, part_name FROM projects
+        WHERE project_name=%s"""
+values = (DIALOG.project_zi.value, )
+result, err = execute_query(CONNECTION, query, values)
+```
+
+With:
+
+```{code-block} python
+def execute_query(connection, query, values):
+  cursor = connection.cursor(buffered=True, dictionary=True)
+  err = None
+  try:
+    cursor.execute(query, values)
+    result = cursor.fetchone()
+    print("Query successful")
+  except Error as err:
+    print(f"Error: '{err}'")
+    return None, err
+  
+  cursor.close()
+  return result, err
+```
+
+As specified in `connection.cursor()` above, the result is a dictionary, e.g. `{'company_name': 'Carl Zeiss GOM Metrology GmbH', 'department_name': 'A2', 'part_name': 'ZEISS Training Object'}`.
+
+#### Inserting / Updating
+
+Both inserting a new and updating an existing table row are based on [MySQLCursor.execute()](https://dev.mysql.com/doc/connector-python/en/connector-python-api-mysqlcursor-execute.html) and [MySQLConnection.commit()](https://dev.mysql.com/doc/connector-python/en/connector-python-api-mysqlconnection-commit.html) &mdash;
+
+Inserting:
+
+```{code-block} python
+# New project, insert
+query = """INSERT INTO projects
+        (project_name, company_name, department_name, part_name)
+        VALUES (%s, %s, %s, %s)"""
+values = (DIALOG.project_zi.value, DIALOG.company_zi.value, DIALOG.department_zi.value, DIALOG.part_zi.value)
+result, err = execute_commit(CONNECTION, query, values)
+```
+
+Updating:
+
+```{code-block} python
+# Project already exists, update
+query = """UPDATE projects SET company_name=%s, department_name=%s, part_name=%s
+        WHERE project_name=%s;"""
+values = (DIALOG.company_zi.value, DIALOG.department_zi.value, DIALOG.part_zi.value, DIALOG.project_zi.value)
+result, err = execute_commit(CONNECTION, query, values)
+```
+
+Both transactions use the function `execute_commit()`:
+
+```{code-block} python
+def execute_commit(connection, query, values):
+  cursor = connection.cursor(buffered=True)
+  err = None
+  try:
+    cursor.execute(query, values)
+    connection.commit()
+    print("Query successful")
+  except Error as err:
+    print(f"Error: '{err}'")
+    return None, err
+    
+  cursor.close()
+  return cursor, err
+```
+
+#### Deleting
+
+Deleting a table row implemented using `execute_query()`. 
+
+```{code-block} python
+query = """DELETE FROM projects WHERE project_name=%s"""
+values = (DIALOG.project_zi.value, )
+result, err = execute_query(CONNECTION, query, values)
+```
+
+## Related
+
+* How-to: [User-defined Dialogs](https://zeissiqs.github.io/zeiss-inspect-addon-api/2025/howtos/python_api_introduction/user_defined_dialogs.md)

AppExamples/misc/SQLExample/doc/README.md

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+## SQLExample
+
+This App is part of the [ZEISS INSPECT Python API App Examples](https://github.com/ZEISS/zeiss-inspect-app-examples/tree/main/AppExamples).
+
+See [App documentation](Documentation.md) for details.
+
+You can [download this App](https://software-store.zeiss.com/products/apps/SQLExample) from the [ZEISS Quality Software Store](https://software-store.zeiss.com).
+
+The ZEISS INSPECT App develomment documentation can be found on [ZEISS IQS GitHub](https://zeissiqs.github.io/zeiss-inspect-addon-api/2025/index.html).