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<concept id="GUID-271E14D1-7B9B-5048-B1F0-1E25B4EA4E16" xml:lang="en"><title>SqlExample: Creating and Querying an SQL Database</title><shortdesc>This example application demonstrates the use of the SQL
API for creating and querying a database.</shortdesc><prolog><metadata><keywords/></metadata></prolog><conbody>
<section id="GUID-8941D325-DE9F-571B-9EAB-C8F675155EEE"><title>Description</title> <p><b>Creating the database</b> </p> <p>You can create two types
of databases; secure and non-secure. </p> <ul>
<li id="GUID-3C94A459-7CD3-5B6C-94D9-235F714FD53E"><p> <b>Non-secure
database:</b> A database that can be accessed and updated by any program
since no security policy is provided. </p> </li>
<li id="GUID-1D128D45-7D64-5BB3-A350-FB13CBD4CEE6"><p> <b>Secure database:</b> A database with static policy defined and therefore can be accessed
by authorized clients with specific capabilities. </p> </li>
</ul> <p><b>Creating a non-secure database</b> </p> <p>The application
first creates an <xref href="GUID-4688F6B7-E1B0-37CF-BAA2-C6BD103D4FDF.dita"><apiname>RSqlDatabase</apiname></xref> object and creates
a non-secure SQL database using the <xref href="GUID-4688F6B7-E1B0-37CF-BAA2-C6BD103D4FDF.dita#GUID-4688F6B7-E1B0-37CF-BAA2-C6BD103D4FDF/GUID-0F4435A7-C28C-342F-AC90-73FABDE6F5DD"><apiname>RSqlDatabase::Create()</apiname></xref> function. The database is then closed. Finally the database is deleted
using the <xref href="GUID-4688F6B7-E1B0-37CF-BAA2-C6BD103D4FDF.dita#GUID-4688F6B7-E1B0-37CF-BAA2-C6BD103D4FDF/GUID-27BE67CC-037F-3533-A3B4-E3CC4879EA1C"><apiname>RSqlDatabase::Delete()</apiname></xref> function. </p> <p>The format for naming the non-secure database would be the following: </p> <codeblock id="GUID-B8E067E8-99B1-56EF-9646-589D38156F90" xml:space="preserve">X:&lt;path&gt;&lt;database-name&gt;.db</codeblock> <p>where, <codeph>X</codeph> is the writable drive on the device
or the emulator. </p> <p>If path is not specified, it returns the <codeph>KErrArgument</codeph> error, and if the specified path is not writable
by SQL server, the application returns <codeph>KErrPermission</codeph> error. In this example, the application will create the database
in its own data area, pass a handle to the database to enable the
data manipulation by the SQL server. </p> <p><note> You cannot create
two databases with the same name in a location </note></p><p><b>Related
APIs</b></p><ul>
<li><p><xref href="GUID-4688F6B7-E1B0-37CF-BAA2-C6BD103D4FDF.dita"><apiname>RSqlDatabase</apiname></xref> - A handle to a SQL database.</p></li>
<li><p><xref href="GUID-4688F6B7-E1B0-37CF-BAA2-C6BD103D4FDF.dita#GUID-4688F6B7-E1B0-37CF-BAA2-C6BD103D4FDF/GUID-0F4435A7-C28C-342F-AC90-73FABDE6F5DD"><apiname>RSqlDatabase::Create()</apiname></xref></p></li>
<li><p><xref href="GUID-4688F6B7-E1B0-37CF-BAA2-C6BD103D4FDF.dita#GUID-4688F6B7-E1B0-37CF-BAA2-C6BD103D4FDF/GUID-27BE67CC-037F-3533-A3B4-E3CC4879EA1C"><apiname>RSqlDatabase::Delete()</apiname></xref></p></li>
</ul> <p><b>Creating a secure database</b> </p> <p>To create a secure
database, you need to provide the following: </p> <ul>
<li id="GUID-AF260BF8-D103-5A08-8BF4-3B8F9F658DBF"><p>UID of the application </p> </li>
<li id="GUID-BCA90A2B-241A-5636-9A2C-080DF6EAAF61"><p>security policy </p> </li>
</ul> <p><b>UID </b> </p> <p>You need to use the UID of the example
application to name the database. </p> <p>The format for naming the
database would be the following: </p> <codeblock id="GUID-768E0B87-B08B-5484-AED0-072D3840CC5B" xml:space="preserve">X:&lt;UID&gt;&lt;name&gt;.db</codeblock> <p>where, </p> <ul>
<li id="GUID-328D11AC-814B-532C-8FEA-A0BB467A0CC2"><p> <codeph>X</codeph> is the drive in which the database is created </p> </li>
<li id="GUID-12C3F6BD-2E50-5FFE-8B1C-2B73A40C88E6"><p> <codeph>UID</codeph> is the UID of the application that creates the database </p> </li>
<li id="GUID-3FA9C3C5-903B-58CD-B509-335686E72BD4"><p> <codeph>name</codeph> is any valid database name. You should not specify the complete
path of the database. </p> </li>
</ul> <p>To successfully create and use a secure database, you must
have appropriate capabilities such as <codeph>READUSERDATA</codeph>, <codeph>WRITEUSERDATA</codeph>. The example application uses <codeph>NETWORKCONTROL</codeph> capablity along with above specified capabilities. </p> <p> <note>If the given UID does not match with that of client application
(in this case, the SQL example application) the attempts to create
the database fails.</note> </p> <p><b>Security policy </b> </p> <p>To create a secure database, you need to initially set up a container
that has a set of security policies (<xref href="GUID-81A285F6-3F87-3E77-9426-61BB16BC7109.dita"><apiname>TSecurityPolicy</apiname></xref>), and pass it to the <xref href="GUID-4688F6B7-E1B0-37CF-BAA2-C6BD103D4FDF.dita#GUID-4688F6B7-E1B0-37CF-BAA2-C6BD103D4FDF/GUID-0F4435A7-C28C-342F-AC90-73FABDE6F5DD"><apiname>RSqlDatabase::Create()</apiname></xref> function.
The <xref href="GUID-81A285F6-3F87-3E77-9426-61BB16BC7109.dita"><apiname>TSecurityPolicy</apiname></xref> object defines what capabilities
the calling application must have in order to perform a specific database
operation. To cross check if the database security policy matches
with the policy used when the database was created, the <xref href="GUID-4688F6B7-E1B0-37CF-BAA2-C6BD103D4FDF.dita#GUID-4688F6B7-E1B0-37CF-BAA2-C6BD103D4FDF/GUID-43E42D5C-62B8-34A7-AF2E-D62432DDB9DE"><apiname>RSqlDatabase::GetSecurityPolicy()</apiname></xref> function is called. </p><p><b>Related APIs</b></p><ul>
<li><p><xref href="GUID-4688F6B7-E1B0-37CF-BAA2-C6BD103D4FDF.dita#GUID-4688F6B7-E1B0-37CF-BAA2-C6BD103D4FDF/GUID-0F4435A7-C28C-342F-AC90-73FABDE6F5DD"><apiname>RSqlDatabase::Create()</apiname></xref></p></li>
<li><p><xref href="GUID-4688F6B7-E1B0-37CF-BAA2-C6BD103D4FDF.dita#GUID-4688F6B7-E1B0-37CF-BAA2-C6BD103D4FDF/GUID-43E42D5C-62B8-34A7-AF2E-D62432DDB9DE"><apiname>RSqlDatabase::GetSecurityPolicy()</apiname></xref></p></li>
<li><p><xref href="GUID-81A285F6-3F87-3E77-9426-61BB16BC7109.dita"><apiname>TSecurityPolicy</apiname></xref> - Class representing a generic
security policy</p></li>
</ul> <p><b>Copying one database to another</b> </p> <p>The example
copies one database to another using the <xref href="GUID-4688F6B7-E1B0-37CF-BAA2-C6BD103D4FDF.dita#GUID-4688F6B7-E1B0-37CF-BAA2-C6BD103D4FDF/GUID-D8B48367-D20B-337E-B41A-1E02119D91D6"><apiname>RSqlDatabase::Copy()</apiname></xref> function. If the database was created using a specific UID, then
only the application with same UID, can perform the copy operation. </p> <p><note> In this example, copy function is essentially a <i>file
copy</i> as the client does a copy within its data cage. The copy
operation should ideally fail if the destination database already
exists. An application with appropriate permissions can use the file
system to copy the database.</note> </p><p><b>Related APIs</b></p><ul>
<li><p><xref href="GUID-4688F6B7-E1B0-37CF-BAA2-C6BD103D4FDF.dita#GUID-4688F6B7-E1B0-37CF-BAA2-C6BD103D4FDF/GUID-D8B48367-D20B-337E-B41A-1E02119D91D6"><apiname>RSqlDatabase::Copy()</apiname></xref></p></li>
</ul> <p><b>Attaching the database</b> </p> <p>The example application
then demonstrates attaching two databases. In this example, a non-secure
database is attached to a secure database. The attached database is
later read from and written to, and the secure database is also written
to before the two databases are deleted using the <xref href="GUID-4688F6B7-E1B0-37CF-BAA2-C6BD103D4FDF.dita#GUID-4688F6B7-E1B0-37CF-BAA2-C6BD103D4FDF/GUID-27BE67CC-037F-3533-A3B4-E3CC4879EA1C"><apiname>RSqlDatabase::Delete()</apiname></xref> function. </p><p><b>Related APIs</b></p><ul>
<li><p><xref href="GUID-4688F6B7-E1B0-37CF-BAA2-C6BD103D4FDF.dita#GUID-4688F6B7-E1B0-37CF-BAA2-C6BD103D4FDF/GUID-27BE67CC-037F-3533-A3B4-E3CC4879EA1C"><apiname>RSqlDatabase::Delete()</apiname></xref></p></li>
</ul> <p><b>Querying the database</b> </p> <p>The example then demonstrates
how to prepare and execute a query. </p> <p><b>Simple query</b> </p> <p>A simple query statement is prepared and executed using the <codeph>CSqlExample::DataTypesQueryL()</codeph> function. </p> <p><b>Query
with a large parameter and writing using streaming</b> </p> <p>A query
with a large parameter is prepared, executed and the results are written
to <xref href="GUID-6313887C-8DE0-3702-BF4B-0622BAB2EE8E.dita"><apiname>RSqlParamWriteStream</apiname></xref> stream. A table containing
fields of data types; integer, 64-bit integer, float, text and binary
is created. It inserts two records into the table and implements the <xref href="GUID-E7B775B0-A609-313A-8BFD-375C81D782A5.dita"><apiname>TSqlScalarFullSelectQuery</apiname></xref> function for 64 bit integer (F2)
and text (F4) fields and checks the returned value. The query for
the data type which the column does not hold is executed, only to
show that this is possible. For example, if a column holding the integer
value 1000 is queried as real, it would return <codeph>1000.00</codeph>. </p><p><b>Related APIs</b></p><ul>
<li><p><xref href="GUID-6313887C-8DE0-3702-BF4B-0622BAB2EE8E.dita"><apiname>RSqlParamWriteStream</apiname></xref> - The write stream
interface.</p></li>
<li><p><xref href="GUID-E7B775B0-A609-313A-8BFD-375C81D782A5.dita"><apiname>TSqlScalarFullSelectQuery</apiname></xref> - TSqlScalarFullSelectQuery
interface is used for executing <codeph>SELECT</codeph> sql queries,
which return a single row consisting of a single column value.</p></li>
</ul> <p><b>Query returning data being read using streaming</b> </p> <p>The example lastly demonstrates how to prepare and execute a
query which returns the data, and read that data from the data stream
(<xref href="GUID-35BF7B4A-C4F7-3215-B5DF-6D0682247976.dita"><apiname>RSqlColumnReadStream</apiname></xref>). The read stream interface
class is used for reading a large amount of binary or text data from
the column. </p><p><b>Related APIs</b></p><ul>
<li><p><xref href="GUID-35BF7B4A-C4F7-3215-B5DF-6D0682247976.dita"><apiname>RSqlColumnReadStream</apiname></xref> - The read stream interface.</p></li>
</ul> </section>
<section id="GUID-EA613161-C0ED-42AD-96D5-DBC9A13643E4"><title>Download</title> <p>Click on the following link to download the example: <xref href="guid-6013a680-57f9-415b-8851-c4fa63356636/zips/guid-ef83061e-0e34-482b-bfcf-267d8972e786.zip" scope="external">SqlExample.zip</xref></p><p>Click: <xref href="guid-6013a680-57f9-415b-8851-c4fa63356636/guid-ef83061e-0e34-482b-bfcf-267d8972e786.html" scope="peer">browse</xref> to view the example code.</p> </section>
<section id="GUID-E5E5C7EA-7E69-42A9-A51C-9B8C0B596605"><title>Class
summary</title><ul>
<li><p><xref href="GUID-4688F6B7-E1B0-37CF-BAA2-C6BD103D4FDF.dita"><apiname>RSqlDatabase</apiname></xref></p></li>
<li><p><xref href="GUID-0176BF07-DF94-3259-8F90-DE030E35CE9A.dita"><apiname>RSqlStatement</apiname></xref></p></li>
<li><p><xref href="GUID-35BF7B4A-C4F7-3215-B5DF-6D0682247976.dita"><apiname>RSqlColumnReadStream</apiname></xref></p></li>
<li><p><xref href="GUID-6313887C-8DE0-3702-BF4B-0622BAB2EE8E.dita"><apiname>RSqlParamWriteStream</apiname></xref></p></li>
<li><p><xref href="GUID-56C52D43-C4A9-3B31-B154-CA1E77693F57.dita"><apiname>RSqlSecurityPolicy</apiname></xref></p></li>
<li><p><xref href="GUID-E7B775B0-A609-313A-8BFD-375C81D782A5.dita"><apiname>TSqlScalarFullSelectQuery</apiname></xref></p></li>
</ul></section>
<section id="GUID-AC702731-D7EE-563C-8AE9-2CFAB58AD97C"><title>Build</title> <p>The Symbian build process describes how to build an application. </p> <p>The Sql example builds an executable called <filepath>sqlexample.exe</filepath> in the standard location (<filepath>\epoc32\release\winscw\</filepath> <i>&lt;build_variant&gt;</i> for CodeWarrior). After launching the
executable depending on the emulator, you may need to task away from
the app launcher or shell screen to view the console. </p> </section>
</conbody><related-links>
<link href="GUID-582CAA4A-1240-5138-983D-D9C6EEAF5566.dita"><linktext>SQL
Tutorials</linktext></link>
</related-links></concept>