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# SFDatabases.Database service

The Database service provides access to databases either embedded or described in Base documents. This service provides methods to:

- Get access to data in database tables.

- Run SELECT queries and perform aggregate functions.

- Run SQL action statements such as INSERT, UPDATE, DELETE, etc.

Each instance of the Database service represents a single database and gives access to its tables, queries and data.

This service does not provide access to forms or reports in the Base document that contains the database. To access forms in a Base document, refer to the method FormDocuments of the Base service.

All exchanges between this service and the database are done using SQL only.

SQL statements may be run in direct or indirect mode. In direct mode the statement is transferred to the database engine without any syntax checking or review.

The provided interfaces include simple tables and queries lists, as well as access to database data.

To make SQL statements more readable, you may use square brackets "[ ]" to enclose names of tables, queries and fields instead of using other enclosing characters that may be exclusive to certain Relational Database Management Systems (RDBMS). But beware that enclosing characters are mandatory in this context.

## Service invocation

### 语法:

To create a instance of the Database service you can use the CreateScriptService method:

CreateScriptService("SFDatabases.Database", [filename: str], [registrationname], [readonly], [user, [password]]): svc

In the syntax described above you can use either "SFDatabases.Database" or simply "Database" as the first argument of the CreateScriptService method.

### 参数:

filename: The name of the Base file. Must be expressed using SF_FileSystem.FileNaming notation.

registrationname: The name of a registered database. If filename is provided, this argument should not be used.

Conversely, if a registrationname is specified, the filename parameter should not be defined.

readonly: Determines if the database will be opened as readonly (Default = True).

user, password: Additional connection parameters to the database server.

### 示例:

##### 在BASIC中

          GlobalScope.BasicLibraries.LoadLibrary("ScriptForge")
          Dim myDatabase as Object
          Set myDatabase = CreateScriptService("Database", "/home/user/Documents/myDB.odb")
          ' Run queries, SQL statements, ...
          myDatabase.CloseDatabase()

##### 在Python中

          from scriptforge import CreateScriptService
          myDatabase = CreateScriptService("Database", "/home/user/Documents/myDB.odb")
          # Run queries, SQL statements, ...
          myDatabase.CloseDatabase()

## Accessing Databases with the UI Service

It is also possible to access the database associated with a Base document using the ScriptForge.UI service, as shown in the examples below:

##### 在BASIC中

          Dim myDoc As Object, myDatabase As Object, ui As Object
          Set ui = CreateScriptService("UI")
          Set myDoc = ui.OpenBaseDocument("/home/user/Documents/myDB.odb")
          ' User and password are supplied below, if needed
          Set myDatabase = myDoc.GetDatabase()
          ' Run queries, SQL statements, ...
          myDatabase.CloseDatabase()
          myDoc.CloseDocument()

##### 在Python中

          ui = CreateScriptService("UI")
          doc = ui.OpenBaseDocument("/home/user/Documents/myDB.odb")
          # User and password are supplied below, if needed
          myDatabase = doc.GetDatabase()
          # Run queries, SQL statements, ...
          myDatabase.CloseDatabase()
          doc.CloseDocument()

The GetDatabase method used in the example above is part of ScriptForge's Base service.

## Properties

Name | Readonly | Type | Description
Queries | Yes | Array of strings | The list of stored queries.
Tables | Yes | Array of strings | The list of stored tables.
XConnection | Yes | XConnection | The UNO object representing the current database connection.
XMetaData | Yes | XDatabaseMetaData | The UNO object representing the metadata describing the database system attributes.

List of Methods in the Database Service
CloseDatabase DAvg DCount | DMin DMax DSum | DLookup GetRows RunSql

## CloseDatabase

Closes the current database connection.

### 语法:

db.CloseDatabase()

### 示例:

        myDatabase.CloseDatabase() ' Basic

        myDatabase.CloseDatabase() # Python

## DAvg, DCount, DMin, DMax, DSum

Computes the given aggregate function on a field or expression belonging to a table.

Optionally, a SQL WHERE clause can be specified as a filter that will be applied prior to the aggregate function.

### 语法:

db.DAvg(expression: str, tablename: str, [criteria: str]): any

db.DCount(expression: str, tablename: str, [criteria: str]): any

db.DMin(expression: str, tablename: str, [criteria: str]): any

db.DMax(expression: str, tablename: str, [criteria: str]): any

db.DSum(expression: str, tablename: str, [criteria: str]): any

### 参数:

expression: A SQL expression in which the field names are surrounded with square brackets.

tablename: A table name (without square brackets).

criteria: A WHERE clause without the "WHERE" keyword, in which field names are surrounded with square brackets.

### 示例:

The example below assumes the file Employees.odb has a table named EmployeeData.

##### 在BASIC中

          GlobalScope.BasicLibraries.LoadLibrary("ScriptForge")
          Dim myDB as Variant
          Set myDB = CreateScriptService("Database", "/home/user/Databases/Employees.odb")
          ' Counts the number of employees in the table
          MsgBox myDB.DCount("[ID]", "EmployeeData")
          ' Returns the sum of all salaries in the table
          MsgBox myDB.DSum("[Salary]", "EmployeeData")
          ' Below are some examples of how tables can be filtered
          MsgBox myDB.DCount("[ID]", "EmployeeData", "[Position] = 'Manager'")
          MsgBox myDB.DCount("[ID]", "EmployeeData", "[Position] = 'Sales' AND [City] = 'Chicago'")
          MsgBox myDB.DCount("[ID]", "EmployeeData", "[FirstName] LIKE 'Paul%'")

##### 在Python中

          myDB = CreateScriptService("Database", "/home/user/Databases/Employees.odb")
          bas = CreateScriptService("Basic")
          bas.MsgBox(myDB.DCount("[ID]", "EmployeeData"))
          bas.MsgBox(myDB.DSum("[Salary]", "EmployeeData"))
          bas.MsgBox(myDB.DCount("[ID]", "EmployeeData", "[Position] = 'Manager'"))
          bas.MsgBox(myDB.DCount("[ID]", "EmployeeData", "[Position] = 'Sales' AND [City] = 'Chicago'"))
          bas.MsgBox(myDB.DCount("[ID]", "EmployeeData", "[FirstName] LIKE 'Paul%'"))

## DLookup

Computes a SQL expression on a single record returned by a WHERE clause defined by the Criteria parameter.

If the query returns multiple records, only the first one is considered. Use the OrderClause parameter to determine how query results are sorted.

### 语法:

db.DLookup(expression: str, tablename: str, [criteria:str], [orderclause: str]): any

### 参数:

expression: A SQL expression in which the field names are surrounded with square brackets.

tablename: A table name (without square brackets).

criteria: A WHERE clause without the "WHERE" keyword, in which field names are surrounded with square brackets.

orderclause: An ORDER BY clause without the "ORDER BY" keywords. Field names should be surrounded with square brackets.

### 示例:

##### 在BASIC中

          MsgBox myDB.DLookup("[FirstName]", "EmployeeData", Criteria := "[LastName] LIKE 'Smith'", OrderClause := "[FirstName] DESC")
          MsgBox myDB.DLookup("[Salary]", "EmployeeData", Criteria := "[ID] = '3'")
          MsgBox myDB.DLookup("[Quantity] * [Value]", "Sales", Criteria := "[SaleID] = '5014'")

##### 在Python中

          bas = CreateScriptService("Basic")
          bas.MsgBox(myDB.DLookup("[FirstName]", "EmployeeData", criteria = "[LastName] LIKE 'Smith'", orderclause = "[FirstName] DESC"))
          bas.MsgBox(myDB.DLookup("[Salary]", "EmployeeData", criteria = "[ID] = '3'"))
          bas.MsgBox(myDB.DLookup("[Quantity] * [Value]", "Sales", criteria = "[SaleID] = '5014'"))

## GetRows

Stores the contents of a table or the results of a SELECT query or of an SQL statement in a two-dimensional array. The first index in the array corresponds to the rows and the second index refers to the columns.

An upper limit can be specified to the number of returned rows. Optionally column names may be inserted in the first row of the array.

The returned array will be empty if no rows are returned and the column headers are not required.

### 语法:

db.GetRows(sqlcommand: str, directsql: bool = False, header: bool = False, maxrows: int = 0): any

### 参数:

sqlcommand: A table or query name (without square brackets) or a SELECT SQL statement.

directsql: When True, the SQL command is sent to the database engine without pre-analysis. Default is False. This argument is ignored for tables. For queries, the applied option is the one set when the query was defined.

header: When True, the first row of the returned array contains the column headers.

maxrows: The maximum number of rows to return. The default is zero, meaning there is no limit to the number of returned rows.

### 示例:

Below are a few examples of how the GetRows method can be used:

##### 在BASIC中

          Dim queryResults as Variant
          ' Returns all rows in the table with column headers
          queryResults = myDB.GetRows("EmployeeData", Header := True)
          ' Returns the first 50 employee records ordered by the 'FirstName' field
          queryResults = myDB.GetRows("SELECT * FROM EmployeeData ORDER BY [FirstName]", MaxRows := 50)

##### 在Python中

          queryResults = myDB.GetRows("EmployeeData", header = True)
          queryResults = myDB.GetRows("SELECT * FROM EmployeeData ORDER BY [FirstName]", maxrows = 50)

## RunSql

Executes an action query of an SQL statement such as creating a table, as well as inserting, updating and deleting records.

The method returns True when successful.

The RunSql method is rejected with an error message in case the database was previously opened in read-only mode.

### 语法:

db.RunSql(sqlcommand: str, directsql: bool = False): bool

### 参数:

sqlcommand: A query name (without square brackets) or a SQL statement.

directsql: When True, the SQL command is sent to the database engine without pre-analysis. (Default = False). For queries, the applied option is the one set when the query was defined.

### 示例:

##### 在BASIC中

          myDatabase.RunSql("INSERT INTO [EmployeeData] VALUES(25, 'Smith', 'John')", DirectSQL := True)

##### 在Python中

          myDatabase.RunSql("INSERT INTO [EmployeeData] VALUES(25, 'Smith', 'John')", directsql = True)

All ScriptForge Basic routines or identifiers that are prefixed with an underscore character "_" are reserved for internal use. They are not meant be used in Basic macros or Python scripts.

相关主题

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SFDocuments.Form service

ScriptForge.UI service