Add a method on Statement to get the declared type of a column.

include/SQLiteCpp/Statement.h

@@ -643,6 +643,24 @@ class Statement
      */
     int getColumnIndex(const char* apName) const;
 
+
+    /**
+     * @brief Return the declared type of the specified result column for a SELECT statement.
+     *
+     *  This is the type given at creation of the column and not the actual data type.
+     *  SQLite stores data types dynamically for each value and not per column.
+     *
+     * @param[in] aIndex    Index of the column in the range [0, getColumnCount()).
+     * 
+     *  Throw an exception if the type can't be determined because:
+     *  - the specified index is out of the [0, getColumnCount()) range
+     *  - the statement is not a SELECT query
+     *  - the column at aIndex is not a table column but an expression or subquery
+     */
+    const char * getColumnDeclaredType(const int aIndex) const;
+
+
+
     ////////////////////////////////////////////////////////////////////////////
 
     /// Return the UTF-8 SQL Query.

src/Statement.cpp

@@ -296,6 +296,20 @@ int Statement::getColumnIndex(const char* apName) const
     return (*iIndex).second;
 }
 
+const char * Statement::getColumnDeclaredType(const int aIndex) const
+{
+    checkIndex(aIndex);
+    const char * result = sqlite3_column_decltype(mStmtPtr, aIndex);
+    if (!result)
+    {
+        throw SQLite::Exception("Could not determine declared column type.");
+    }
+    else
+    {
+        return result;
+    }
+}
+
 int Statement::getBindParameterCount() const noexcept
 {
     return sqlite3_bind_parameter_count(mStmtPtr);

tests/Statement_test.cpp

@@ -918,6 +918,32 @@ TEST(Statement, getName)
 #endif
 }
 
+TEST(Statement, getColumnDeclaredType)
+{
+    // Create a new database
+    SQLite::Database db(":memory:", SQLite::OPEN_READWRITE | SQLite::OPEN_CREATE);
+    EXPECT_EQ(0, db.exec("CREATE TABLE test (id INTEGER PRIMARY KEY, msg TEXT, value DOUBLE)"));
+
+    SQLite::Statement query(db, "SELECT *, 1 FROM test");
+
+    const std::string decltype0 = query.getColumnDeclaredType(0);
+    const std::string decltype1 = query.getColumnDeclaredType(1);
+    const std::string decltype2 = query.getColumnDeclaredType(2);
+    EXPECT_EQ("INTEGER", decltype0);
+    EXPECT_EQ("TEXT", decltype1);
+    EXPECT_EQ("DOUBLE", decltype2);
+
+    // The column at index 3 is not a table column.
+    EXPECT_THROW(query.getColumnDeclaredType(3), SQLite::Exception);
+
+    // Index out of bounds.
+    EXPECT_THROW(query.getColumnDeclaredType(4), SQLite::Exception);
+
+    // Not a select statement.
+    SQLite::Statement pragma(db,"PRAGMA compile_options");
+    EXPECT_THROW(pragma.getColumnDeclaredType(0), SQLite::Exception);
+}
+
 #if __cplusplus >= 201402L || (defined(_MSC_VER) && _MSC_VER >= 1900)
 TEST(Statement, getColumns)
 {