MATLAB DATABASE TOOLBOX RELEASE NOTES Guide de l'utilisateur télécharger pdf (Page 383)

100

101

Selecting Data Using the exec Function

6-41

• A cursor stays open until you close it using the close function.

Working with Microsoft Excel

For Microsoft Excel, tables in sqlquery are Excel worksheets. By default, some

worksheet names include $. To select data from a worksheet with this name format, use

an SQL statement of the form select * from "Sheet1$" (or 'Sheet1$') .

Database Considerations

• The order of records in your database is not constant. Use values in column names to

identify records. Use the SQL ORDER BY command to sort records.

• Before you modify database tables, ensure that the database is not open for editing. If

you try to edit the database while it is open, you receive this MATLAB error:

[Vendor][ODBC Driver] The database engine could not lock

table 'TableName' because it is already in use by

another person or process.

• You might experience issues with text field formats in the Microsoft SQL Server

database management system. Workarounds for these issues are as follows:

• Convert fields of format NVARCHAR, TEXT, NTEXT, and VARCHAR to CHAR in the

database.

• Use sqlquery to convert data to VARCHAR. For example, run a sqlquery

statement of the form 'select convert(varchar(20),field1) from

table1'.

• The PostgreSQL database management system supports multidimensional fields, but

SQL select statements fail when retrieving these fields unless you specify an index.

• Some databases require that you include a symbol, such as #, before and after a date

in a query as follows:

curs = exec(conn,'select * from mydb where mydate > #03/05/2005#')

• Some databases require that you include a symbol, such as #, before and after a date

in a query as follows:

curs = exec(conn,'select * from mydb where mydate > #03/05/2005#')

Commentaires sur ces manuels

Pas de commentaire

MATLAB DATABASE TOOLBOX RELEASE NOTES Guide de l'utilisateur Page 383

Commentaires sur ces manuels

Produits connexes et manuels pour Logiciel MATLAB DATABASE TOOLBOX RELEASE NOTES