Skip to content

Embedded SQL API

In DataFlex 2023, we introduced a new way to work directly with SQL statements. A new engine for executing statements is built into the runtime that puts result sets directly into native DataFlex types. This means results can now go directly into structs, multidimensional arrays and variants with proper type conversions done automatically. Parameterized queries now support named parameters and only a single class/object is needed for executing queries. Studio support for working with SQL statements is improved by adding syntax highlighting, code sense and a query test tool for SQL statements.

SQL Executor

The cSQLExecutor package provides the API for executing SQL statements from DataFlex. It can be used as a global singleton object for executing queries within a single line of code or with an instance per connection or per prepared statement. Result sets are immediately fetched and made available in native types (structs, arrays, variants) using a flexible and smart API. Prepared statements with named parameters are supported. There are APIs for querying the result set structure and the parameters to build dynamic applications.

To get full Studio support use the @SQL string or include queries from separate files using Include_Text.

The engine of the cSQLExecutor is inside the runtime and this is exposed in the abstract cBaseSQLExecutor class. The runtime works directly with ODBC and relies on the connectivity kits to manage the connection. This means that the cSQLExecutor will work with the ODBC based drivers (MS SQL, DB2 and ODBC).

SQL in the DataFlex language

An important part of SQL is the query language. To improve SQL-ness of the language, we have incorporated SQL statements into our language. This goes for partial statements as well as full SQL statements. Currently the places where SQL statements are allowed (SQL Filters and Embedded SQL) use regular strings. To identify a SQL query string, the @SQL prefix was added and multi-line strings are supported now.

Example:

Embedded SQL Select

Using the cSQLExecutor class / object

Setting up the database connection

The database connection to the SQL database can be setup by using a Managed Connection. The psConnectionId property of cSQLExecutor should be set to one of the Connection IDs defined in the SQL Connection Manager of your workspace.

Example:

Set psConnectionId of ghoSQLExecutor to "MyConnectionID"

pbIsConnected (pbIsConnected) can be checked to test if a connection is initialized.

Singleton

The simplest way to use the cSQLExecutor is to create a singleton instance within your project. This can be done using the template available in the Create New dialog in the DataFlex Studio: File Menu > New > Other > SQL Executor.

This will create a .pkg file that can be included in a program.

Example:

Use cSQLExecutor.pkg
Object oSQLExecutor is a cSQLExecutor
    Move Self to ghoSQLExecutor
    // Set psConnectionId to "SQLDATA"
End_Object

ghoSQLExecutor is a predefined global variable that can be used to access the SQLExecutor object throughout the program.

Use in WebApps

If you add a cSQLExecutor object in WebApp.src, be sure to make it a child object of the cWebApp object. If you add a cSQLExecutor object before the cWebApp object, it will cause the WebApp to behave like a Windows application rather than a Web Application.

Events

The cSQLExecutor class has the following callback procedures:

  1. Procedure OnSQLError String sSQLState String sSQLMessage
  2. Triggered if an ODBC error occurs. By default a DataFlex error will be generated; implementing this event without a forward send will cancel this error.
  3. sSQLState holds the ODBC error number.

  4. sSQLMessage holds the ODBC error description.

  5. Procedure OnSQLPreExecute String sSQLQuery

  6. Triggered before the beginning of an Execute.

  7. sSQLQuery holds the query string.

  8. Procedure OnSQLPostExecute String sSQLQuery

  9. Triggered after an Execute is finished.
  10. sSQLQuery holds the query string.

Execution of queries

The cSQLExecutor class has the following functions and procedures to prepare and execute a SQL query:

  1. Procedure SQLPrepare String sSQLQuery
  2. Function SQLExecute Returns Variant[]
  3. Procedure SQLExecute
  4. Function SQLExecDirect String sSQLQuery Returns Variant[]
  5. Procedure SQLExecDirect String sSQLQuery

If an ODBC error occurs, OnSQLError is called and the global Err flag will be set.

Direct Execution of Queries

Call SQLExecDirect to execute a SQL query directly. SQLExecDirect can be used in two ways, with or without a result set.

Example of SQLExecDirect with result set:

String[][] aResults
// Fetch results into aResults
Get SQLExecDirect of ghoSQLExecutor @SQL"SELECT
Name,
City,
Zip
FROM Customer" to aResults
// Test for errors
If (not(Err)) Begin
    // Process results here..
End

Example of SQLExecDirect without result set:

// This is normally used for queries without a result set
Integer iAffectedRows
Send SQLExecDirect of ghoSQLExecutor @SQL"UPDATE Customer
SET NAME = 'Thomas Hardy', City = 'London'
WHERE Customer_Number = 1"
// Test for errors
If (not(Err)) Begin
    Get piSQLAffectedRows of ghoSQLExecutor to iAffectedRows
End

Prepared Execution of Queries

SQLPrepare will prepare the query without returning information.

Example:

// Prepare the query
Send SQLPrepare of ghoSQLExecutor @SQL"SELECT
Name,
City,
Zip
FROM Customer"
// Test for errors
If (not(Err)) Begin
    // Execute the query here..
End

Call SQLExecute to execute a prepared SQL query. SQLExecute can be used in two ways, with or without a result set.

Example of SQLExecute with result set:

String[][] aResults
// Prepare the query
Send SQLPrepare of ghoSQLExecutor @SQL"SELECT
Name,
City,
Zip
FROM Customer"
// Test for errors
If (not(Err)) Begin
    // Fetch the results into aResults
    Get SQLExecute of ghoSQLExecutor to aResults
End

Example of SQLExecute without result set:

// This is normally used for queries without a result set
Send SQLPrepare of ghoSQLExecutor @SQL"UPDATE Customer
SET NAME = 'Thomas Hardy', City = 'London'
WHERE Customer_Number = 1"
// Test for errors
If (not(Err)) Begin
    // Execute the query
    Send SQLExecute of ghoSQLExecutor
End

Result Sets

The result sets of a query can be fetched into the following types:

The destination array for String and Variant should be defined as a two-dimensional array. The array for Structs, tWebRow and tDataSourceRow should be defined as a one-dimensional array.

String array example:

String[][] aResults
// Fetch results into aResults
Get SQLExecDirect of ghoSQLExecutor @SQL"SELECT
Name,
City,
Zip
FROM Customer" to aResults
// Test for errors
If (not(Err)) Begin
    // Process results here..
End

This query will result in a two-dimensional array of [100][3] i.e. 100 rows with 3 columns of type string.

Variant array example:

Variant[][] aResults
// Fetch results into aResults
Get SQLExecDirect of ghoSQLExecutor @SQL"SELECT
Name,
City,
Zip
FROM Customer" to aResults
// Test for errors
If (not(Err)) Begin
    // Process results here..
End

This query will result in a two-dimensional array of [100][4] i.e. 100 rows with 4 columns. Note that in this case the column Customer_Number will be of type Integer and the Name, City and Zip columns are of type String.

Struct array example:

// Define the struct
Struct tResult
    String Name
    String City
    String Zip
End_Struct

tResult[] aResults
// Fetch results into aResults
Get SQLExecDirect of ghoSQLExecutor @SQL"SELECT
Name,
City,
Zip
FROM Customer" to aResults
// Test for errors
If (not(Err)) Begin
    // Process results here..
End

This query will result in a one-dimensional array of [100], i.e. 100 rows of struct tResult holding the data.

The cSQLExecutor class also supports fetching result set data directly into tDataSourceRow and tWebRow to make the use of grids very convenient. In combination with column info, one can make grids dynamic with a few lines of code.

tDataSourceRow array example:

tDataSourceRow[] aDataSourceRows
// Fetch results into aDataSourceRows
Get SQLExecDirect of ghoSQLExecutor @SQL"SELECT
Name,
City,
Zip
FROM Customer" to aDataSourceRows
// Test for errors
If (not(Err)) Begin
    // Process results here..
End

This query will result in a one-dimensional array of [100], i.e. 100 rows of struct tDataSourceRow holding the data.

tDataSourceRow array with static grid example:

// The grid object
Object oCJGrid1 is a cCJGrid
    Set Size to 192 517
    Set Location to 6 10

    Object oCJGridColumn1 is a cCJGridColumn
        Set piWidth to 300
        Set psCaption to "Name"
    End_Object

    Object oCJGridColumn2 is a cCJGridColumn
        Set piWidth to 200
        Set psCaption to "City"
    End_Object

    Object oCJGridColumn3 is a cCJGridColumn
        Set piWidth to 60
        Set psCaption to "Zip"
    End_Object
End_Object

// Further in the code
tDataSourceRow[] aDataSourceRows
// Fetch results into aDataSourceRows
Get SQLExecDirect of ghoSQLExecutor @SQL"SELECT
Name,
City,
Zip
FROM Customer" to aDataSourceRows
// Test for errors
If (not(Err)) Begin
    // Initialize the grid, i.e. fill
    Send InitializeData of oCJGrid1 aDataSourceRows
End

tWebRow array example:

tWebRow[] aWebRows
// Fetch results into aWebRows
Get SQLExecDirect of ghoSQLExecutor @SQL"SELECT
Name,
City,
Zip
FROM Customer" to aWebRows
// Test for errors
If (not(Err)) Begin
    // Process results here..
End

This query will result in a one-dimensional array of [100], i.e. 100 rows of struct tWebRow holding the data.

Multiple Result Sets

For multiple result sets, the destination array for String and Variant should be defined as a three-dimensional array and the array for Structs, tWebRow and tDataSourceRow should be defined as a two-dimensional array.

Multiple result set string array example:

String[][][] aStrings
// Fetch results into aStrings
Get SQLExecDirect of ghoSQLExecutor @SQL"SELECT * FROM OrderDetail
SELECT TOP 10 NAME, City, Zip FROM Customer" to aStrings
// Test for errors
If (not(Err)) Begin
    // Process results here..
End

This query will result in a three-dimensional array of [2][n][m] i.e. 2 result sets: the first result set (index 0) with n rows of strings, and the second result set (index 1) with m rows.

The array has the following format: [RESULT SET][ROW][DATA].

Multiple result set tDataSourceRow array example:

tDataSourceRow[][] aDataSourceRows
// Fetch results into aDataSourceRows
Get SQLExecDirect of ghoSQLExecutor @SQL"SELECT * FROM OrderDetail
SELECT TOP 10 NAME, City, Zip FROM Customer" to aDataSourceRows
// Test for errors
If (not(Err)) Begin
    // Initialize the grids, i.e. fill; let's take two grids for example
    Send InitializeData of oCJGrid1 aDataSourceRows[0] // result set 1
    Send InitializeData of oCJGrid2 aDataSourceRows[1] // result set 2
End

This query will result in a two-dimensional array of [2][n] i.e. 2 result sets each containing rows of tDataSourceRow.

Parameterized Queries

To use named parameters in a query, parameter names should have the $ sign as prefix and be enclosed in curly brackets, e.g. ${param_name}. Note: SQLExecDirect cannot handle named parameter queries directly — the named-parameter query should always be prepared first. After SQLPrepare, the parameters can be set and the parameter information can be retrieved.

The following procedure and function are available for parameterized queries:

  • Procedure SQLSetParameter String sParamName Variant Value
  • Function SQLParameterInfo Returns tSQLParamInfo[]

The tSQLParamInfo struct is defined in cSQLExecutor.pkg:

Struct tSQLParamInfo
    String sName
    String sValue
End_Struct

SQLSetParameter example:

String[][] aStrings
// Prepare the query
Send SQLPrepare of ghoSQLExecutor @SQL"SELECT
Name,
City,
Zip FROM Customer
WHERE City = ${City}"
// Test for errors
If (not(Err)) Begin
    // Set the parameter value
    Send SQLSetParameter of ghoSQLExecutor "City" "Miami"
    // Get the result set
    Get SQLExecute of ghoSQLExecutor to aStrings
    // Process results here..
End

SQLParameterInfo example:

tSQLParamInfo[] aParamsInfo
// Prepare the query
Send SQLPrepare of ghoSQLExecutor @SQL"SELECT
Name,
City,
Zip FROM Customer
WHERE City = ${City}"
// Test for errors
If (not(Err)) Begin
    // Set the parameter value
    Send SQLSetParameter of ghoSQLExecutor "City" "Miami"
    // Get the parameters info
    Get SQLParameterInfo of ghoSQLExecutor to aParamsInfo
    // Process results here..
End

Querying Result Set Structure

SQLColumnInfo returns the column information for the result set into an array of tSQLColumnInfo structs. If you want to put the results into a grid, the column information can be used to initialize your grid columns. Always call SQLColumnInfo after a SQLExecute or SQLExecDirect.

The tSQLColumnInfo struct is defined in cSQLExecutor.pkg:

Struct tSQLColumnInfo
    String  sName      // column name (returned)
    Integer iType      // SQL data type of column
    Integer iSize      // Data size of column in table
    Integer iDigits    // Number of digits after the decimal separator
    Boolean bNullable  // Whether column is nullable
End_Struct

SQLColumnInfo example:

String[][] aResults
tSQLColumnInfo[] aSQLColumnsInfo
// Fetch results into aResults
Get SQLExecDirect of ghoSQLExecutor @SQL"SELECT
Name,
City,
Zip
FROM Customer" to aResults
// Test for errors
If (not(Err)) Begin
    // Get the columns info
    Get SQLColumnInfo of ghoSQLExecutor to aSQLColumnsInfo
    // Process results here..
End

This query will result in an aSQLColumnsInfo array with 3 elements holding the information for the columns Name, City and Zip.

Query Tester

A Query Tester has been added to the Studio. It helps you create, test and execute SQL queries and has a Struct Generator.

Read more about the Query Tester.

Include_Text

Include_Text allows .SQL and other text files to be included as constants with a single line of DataFlex code.