sqlite3 columns types

Question

I'm starting a new project that has to convert data from XML to db. XMLs have their own format and cannot be used to fill a db.

I choose to use sqlite, because it is an embedded platform and I need a lightweight library.

I'm struggling with columns types. I wrote the sql below:

static int callback(void *NotUsed, int argc, char **argv, char **azColName)
{
   int i;
   for(i=0; i<argc; i++){
      printf("%s = %s\n", azColName[i], argv[i] ? argv[i] : "NULL");
   }
   printf("\n");
   return 0;
}

static bool exec_sql (sqlite3 *db, char *sql, bool use_callback)
{
    int rc;
    char *zErrMsg = 0;

    // Execute SQL statement
    if (use_callback == true)
    {
        rc = sqlite3_exec(db, sql, callback, 0, &zErrMsg);
    }
    else
    {
        rc = sqlite3_exec(db, sql, NULL, 0, &zErrMsg);
    }

    if( rc != SQLITE_OK )
    {
        fprintf(stderr, "SQL: %s FAIL!!!\nError: %s\n", sql, zErrMsg);
        sqlite3_free(zErrMsg);
        return false;
    }
    return true;
}

int main ( int argc, char *argv[] )
{
    xmlDoc *doc;
    xmlNode *root_element;
    FILE *fw;
    int i, srcidx, next_start;

    sqlite3 *db;
    char *zErrMsg = 0;
    int rc;
    char *sql;

    rc = sqlite3_open("Configuration.db", &db);

    if( rc )
    {
        XML2DB_DEBUG_ERR("Can't open database: %s\n", sqlite3_errmsg(db));

    }
    else
    {
        XML2DB_DEBUG_INFO("Opened database successfully\n");
    }

    sql = "CREATE TABLE Table2("  \
         "ID          INT      NOT NULL PRIMARY KEY," \
         "TABLE_1_ID  INT      FOREGN KEY REFERENCES Table1(ID) NOT NULL ," \ 
         "COLUMN_1    INT[512] NOT NULL,"\
         "COLUMN_2    TEXT     NOT NULL,"\
         "COLUMN_3    BOOLEAN  DEFAULT FALSE);";

    // Execute SQL statement
    exec_sql(db, sql, false);

    sql = "INSERT INTO Models (ID, TABLE_1_ID, COLUMN_1, COLUMN_2, COLUMN_3) "\
          "VALUES (1, 1, '{1,2,3,4,5}', 'blabla', TRUE); ";

    // Execute SQL statement
    exec_sql(db, sql,true);

    sql = "SELECT * FROM Table2;";

    // Execute SQL statement
    exec_sql(db, sql, true);

    sqlite3_close(db);

    return 0;
}

That code works well, but now I found out that sqlite3 does not support boolean and array datatypes.

I wrote, "it works well", because of a SELECT and DBVisualizer can display data and do not give me errors.

So, the questions are:

1. Why sql are executes well even if datatype are not supported and inserted values are not correct?
2. *Is there a feature that can be enable to always check that values of insert are well formatted? *

Answer 1

SQLite uses dynamic typing.

To check data types, use CHECK constraints:

CREATE TABLE Table2(
    ID          INTEGER  PRIMARY KEY,
    TABLE_1_ID  INT      FOREIGN KEY REFERENCES Table1(ID) NOT NULL,
    COLUMN_1    INT[512] NOT NULL
    COLUMN_2    TEXT     NOT NULL   CHECK (typeof(COLUMN_2) = 'text'),
    COLUMN_3    BOOLEAN  DEFAULT 0  CHECK (COLUMN_3 IN (0, 1))
);