private void ProcessDeleteStatement(List <string> tokens, ref QueryResult queryResult)
{
// <Delete Stm> ::= DELETE <From Clause> TABLE <Where Clause>
IntSchTable tableToDeleteFrom = null;
int tableOffset = 0;
for (int i = 1; i < tokens.Count; ++i)
{
if (tokens[i] == "from")
{
tableOffset = i + 1;
break;
}
}
tableToDeleteFrom = GetTable(tokens[tableOffset]);
SQLConditional sqlConditional = ParseWhereClause(tokens);
if (!ValidateColumns(ref queryResult, sqlConditional.GetColumns(), tableToDeleteFrom,
allowWildCard: false))
{
return;
}
tableToDeleteFrom.Delete(sqlConditional);
}
private void ProcessUpdateStatement(List <string> tokens, ref QueryResult queryResult)
{
string nameOfTableToUpdate = tokens[1];
List <string> columnsToUpdate = new List <string>();
List <string> updatedValues = new List <string>();
ParseUpdates(tokens, ref columnsToUpdate, ref updatedValues);
SQLConditional conditional = ParseWhereClause(tokens);
IntSchTable tableToUpdate = GetTable(nameOfTableToUpdate);
// Validate update columns
if (!ValidateColumns(ref queryResult, columnsToUpdate, tableToUpdate, /*allowWildCard=*/ false))
{
return;
}
// Validate conditional columns
List <string> conditionalColumns = conditional.GetColumns();
if (!ValidateColumns(ref queryResult, conditionalColumns, tableToUpdate, /*allowWildCard=*/ false))
{
return;
}
tableToUpdate.Update(columnsToUpdate, updatedValues, conditional);
}
private void ProcessSelectStatement(List <string> tokens, ref QueryResult queryResult)
{
// <Select Stm> ::= SELECT <Columns> <From Clause> <Where Clause> <Group Clause> <Having Clause> <Order Clause>\
IntSchTable tableToSelectFrom = null;
IntSchTable results = null;
List <string> colsToSelect = new List <string>();
List <string> colsToValidate = new List <string>();
int tableOffset = 0;
for (int i = 1; i < tokens.Count; ++i)
{
if (tokens[i] == "from")
{
tableOffset = i + 1;
break;
}
else if (tokens[i] == ",")
{
continue;
}
else if (i + 3 < tokens.Count &&
(tokens[i].ToLower() == "avg" || tokens[i].ToLower() == "max" ||
tokens[i].ToLower() == "min" ||
tokens[i].ToLower() == "sum"))
{
if (tokens[i + 2] == "*")
{
string errorMessage = "Invalid arguments for function " + tokens[i] + "()";
string errorType = "SQL";
queryResult.Error = new InputError(errorType, errorMessage);
return;
}
colsToSelect.Add(tokens[i] + tokens[i + 1] + tokens[i + 2] + tokens[i + 3]);
colsToValidate.Add(tokens[i + 2]);
i += 3;
}
else if (i + 3 < tokens.Count && tokens[i].ToLower() == "count")
{
colsToSelect.Add(tokens[i] + tokens[i + 1] + tokens[i + 2] + tokens[i + 3]);
colsToValidate.Add(tokens[i + 2]);
i += 3;
}
else
{
colsToSelect.Add(tokens[i]);
colsToValidate.Add(tokens[i]);
}
}
string nameOfTableToSelectFrom = tokens[tableOffset];
// Validate Table's existence
for (int i = 0; i < tables.Count; ++i)
{
if (tables[i].Name == nameOfTableToSelectFrom)
{
tableToSelectFrom = tables[i];
break;
}
}
if (tableToSelectFrom == null)
{
string errorMessage = "Could not find table: " + nameOfTableToSelectFrom;
string errorType = "SQL";
queryResult.Error = new InputError(errorType, errorMessage);
return;
}
if (!ValidateColumns(ref queryResult, colsToValidate, tableToSelectFrom, /*allowWildcard=*/ true))
{
return;
}
SQLConditional sqlConditional = ParseWhereClause(tokens);
// Validate conditional
List <string> conditionalColumns = sqlConditional.GetColumns();
if (!ValidateColumns(ref queryResult, conditionalColumns, tableToSelectFrom, /*allowWildCard=*/
false))
{
return;
}
// Execute Selection
results = tableToSelectFrom.Select(colsToSelect, sqlConditional);
queryResult.Results = results;
return;
}