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Add sample code for getColumn() by name

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- sample code provided by #46
 - rework example for better readability
This commit is contained in:
Sébastien Rombauts 2015-04-30 22:08:26 +02:00
parent 7fbfc29677
commit 416958f094
1 changed files with 67 additions and 20 deletions
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87
examples/example1/main.cpp
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@ -83,7 +83,8 @@ private:
int main ()
{
// Basic example (1/6) :
////////////////////////////////////////////////////////////////////////////
// Very basic first example (1/7) :
try
{
// Open a database file in readonly mode
@ -95,8 +96,24 @@ int main ()
std::cout << "SQLite table 'test' exists=" << bExists << "\n";
// Get a single value result with an easy to use shortcut
std::string value = db.execAndGet("SELECT value FROM test WHERE id=2");
const std::string value = db.execAndGet("SELECT value FROM test WHERE id=2");
std::cout << "execAndGet=" << value.c_str() << std::endl;
}
catch (std::exception& e)
{
std::cout << "SQLite exception: " << e.what() << std::endl;
return EXIT_FAILURE; // unexpected error : exit the example program
}
////////////////////////////////////////////////////////////////////////////
// Simple select query - few variations (2/7) :
try
{
// Open a database file in readonly mode
SQLite::Database db(filename_example_db3); // SQLITE_OPEN_READONLY
std::cout << "SQLite database file '" << db.getFilename().c_str() << "' opened successfully\n";
///// a) Loop to get values of column by index, using auto cast to variable type
// Compile a SQL query, containing one parameter (index 1)
SQLite::Statement query(db, "SELECT id as test_id, value as test_val, weight as test_weight FROM test WHERE weight > ?");
@ -105,6 +122,24 @@ int main ()
query.bind(1, 2);
std::cout << "binded with integer value '2' :\n";
// Loop to execute the query step by step, to get one a row of results at a time
while (query.executeStep())
{
// Demonstrates how to get some typed column value (and the equivalent explicit call)
const int id = query.getColumn(0); // = query.getColumn(0).getInt();
//const char* pvalue = query.getColumn(1); // = query.getColumn(1).getText();
const std::string value = query.getColumn(1); // = query.getColumn(1).getText();
const int bytes = query.getColumn(1).size(); // .getColumn(1).getBytes();
const double weight = query.getColumn(2); // = query.getColumn(2).getInt();
std::cout << "row (" << id << ", \"" << value.c_str() << "\"(" << bytes << ") " << weight << ")\n";
}
///// b) Get aliased column names (and original column names if possible)
// Reset the query to use it again
query.reset();
std::cout << "SQLite statement '" << query.getQuery().c_str() << "' reseted (" << query.getColumnCount() << " columns in the result)\n";
// Execute the first step of the query, to get the fist row of results, and name of columns
if (query.executeStep())
{
@ -113,6 +148,7 @@ int main ()
const std::string name1 = query.getColumn(1).getName();
const std::string name2 = query.getColumn(2).getName();
std::cout << "aliased result [\"" << name0.c_str() << "\", \"" << name1.c_str() << "\", \"" << name2.c_str() << "\"]\n";
#ifdef SQLITE_ENABLE_COLUMN_METADATA
// Show how to get origin names of the table columns from which theses result columns come from.
// Requires the SQLITE_ENABLE_COLUMN_METADATA preprocessor macro to be
@ -122,23 +158,34 @@ int main ()
const std::string oname2 = query.getColumn(2).getOriginName();
std::cout << "origin table 'test' [\"" << oname0.c_str() << "\", \"" << oname1.c_str() << "\", \"" << oname2.c_str() << "\"]\n";
#endif
// Demonstrates how to get some typed column value (and the equivalent explicit call)
const int id = query.getColumn(0); // = query.getColumn(0).getInt();
//const char* pvalue = query.getColumn(1); // = query.getColumn(1).getText();
const std::string value2 = query.getColumn(1); // = query.getColumn(1).getText();
const int bytes = query.getColumn(1).getBytes();
const double weight = query.getColumn(2); // = query.getColumn(2).getInt();
std::cout << "row (" << id << ", \"" << value2.c_str() << "\" " << bytes << " bytes, " << weight << ")\n";
// Demonstrates that inserting column value in a std:ostream is natural
std::cout << "row (" << query.getColumn(0) << ", \"" << query.getColumn(1) << "\", " << query.getColumn(2) << ")\n";
}
// Loop to execute the query step by step, to get one a row of results at a time
// Loop to execute the rest of the query step by step, to get one a row of results at a time
while (query.executeStep())
{
// Demonstrates that inserting column value in a std:ostream is natural
std::cout << "row (" << query.getColumn(0) << ", \"" << query.getColumn(1) << "\", " << query.getColumn(2) << ")\n";
}
///// c) Get columns by name
// Reset the query to use it again
query.reset();
std::cout << "SQLite statement '" << query.getQuery().c_str() << "' reseted (" << query.getColumnCount() << " columns in the result)\n";
// Loop to execute the query step by step, to get one a row of results at a time
while (query.executeStep())
{
// Demonstrates how to get column value by aliased name (not the original table names, see above)
const int id = query.getColumn("test_id");
const std::string value = query.getColumn("test_val");
const double weight = query.getColumn("test_weight");
std::cout << "row (" << id << ", \"" << value.c_str() << "\" " << weight << ")\n";
}
///// d) Uses explicit typed getters instead of auto cast operators
// Reset the query to use it again
query.reset();
std::cout << "SQLite statement '" << query.getQuery().c_str() << "' reseted (" << query.getColumnCount () << " columns in the result)\n";
@ -147,14 +194,14 @@ int main ()
std::cout << "binded with string value \"6\" :\n";
// Reuses variables: uses assignement operator in the loop instead of constructor with initialization
int id = 0;
std::string value2;
std::string value;
double weight = 0.0;
while (query.executeStep())
{
id = query.getColumn(0).getInt();
value2 = query.getColumn(1).getText();
value = query.getColumn(1).getText();
weight = query.getColumn(2).getInt();
std::cout << "row (" << id << ", \"" << value2 << "\", " << weight << ")\n";
std::cout << "row (" << id << ", \"" << value << "\", " << weight << ")\n";
}
}
catch (std::exception& e)
@ -164,7 +211,7 @@ int main ()
}
////////////////////////////////////////////////////////////////////////////
// Object Oriented Basic example (2/6) :
// Object Oriented Basic example (3/7) :
try
{
// Open the database and compile the query
@ -181,7 +228,7 @@ int main ()
return EXIT_FAILURE; // unexpected error : exit the example program
}
// The execAndGet wrapper example (3/6) :
// The execAndGet wrapper example (4/7) :
try
{
// Open a database file in readonly mode
@ -201,7 +248,7 @@ int main ()
}
////////////////////////////////////////////////////////////////////////////
// Simple batch queries example (4/6) :
// Simple batch queries example (5/7) :
try
{
// Open a database file in create/write mode
@ -242,7 +289,7 @@ int main ()
remove("test.db3");
////////////////////////////////////////////////////////////////////////////
// RAII transaction example (5/6) :
// RAII transaction example (6/7) :
try
{
// Open a database file in create/write mode
@ -310,7 +357,7 @@ int main ()
remove("transaction.db3");
////////////////////////////////////////////////////////////////////////////
// Binary blob and in-memory database example (6/6) :
// Binary blob and in-memory database example (7/7) :
try
{
// Open a database file in create/write mode