#ifndef QSQLQUERY_H
#define QSQLQUERY_H
#include <QtSql/qsql.h>
#include <QtSql/qsqldatabase.h>
#include <QtCore/qstring.h>
QT_BEGIN_HEADER //声明开始头文件
QT_BEGIN_NAMESPACE //声明开始命名空间
QT_MODULE(Sql)
class QVariant;
class QSqlDriver;
class QSqlError;
class QSqlResult;
class QSqlRecord;
template <class Key, class T> class QMap; //模板类,复杂的结构
class QSqlQueryPrivate;
class Q_SQL_EXPORT QSqlQuery
{
public:
//有参数的能加const的，都加上const
QSqlQuery(QSqlResult *r); //结果作为参数？
QSqlQuery(const QString& query = QString(), QSqlDatabase db = QSqlDatabase());
explicit QSqlQuery(QSqlDatabase db); //显式地？什么意义？参数只有个db
QSqlQuery(const QSqlQuery& other);
QSqlQuery& operator=(const QSqlQuery& other);
~QSqlQuery();
//以下类似没有参数的函数，大都有const后缀。具体内容说明可参考qt帮助文档
bool isValid() const;
bool isActive() const;
bool isNull(int field) const;
int at() const;
QString lastQuery() const;
int numRowsAffected() const;
QSqlError lastError() const;
bool isSelect() const;
int size() const;
const QSqlDriver* driver() const;
const QSqlResult* result() const;
bool isForwardOnly() const;
QSqlRecord record() const;
void setForwardOnly(bool forward);
bool exec(const QString& query);
QVariant value(int i) const;
void setNumericalPrecisionPolicy(QSql::NumericalPrecisionPolicy precisionPolicy);
QSql::NumericalPrecisionPolicy numericalPrecisionPolicy() const;
bool seek(int i, bool relative = false);
bool next();
bool previous();
//有const表示未对数据的值产生改变，，没有const的函数对数据的值产生了改变
#ifdef QT3_SUPPORT
inline QT3_SUPPORT bool prev() { return previous(); }
#endif
bool first();
bool last();
void clear();
// prepared query support
bool exec();
enum BatchExecutionMode { ValuesAsRows, ValuesAsColumns };
bool execBatch(BatchExecutionMode mode = ValuesAsRows);
bool prepare(const QString& query);
void bindValue(const QString& placeholder, const QVariant& val,
QSql::ParamType type = QSql::In);
void bindValue(int pos, const QVariant& val, QSql::ParamType type = QSql::In);
void addBindValue(const QVariant& val, QSql::ParamType type = QSql::In);
QVariant boundValue(const QString& placeholder) const;
QVariant boundValue(int pos) const;
QMap<QString, QVariant> boundValues() const;
QString executedQuery() const;
QVariant lastInsertId() const;
void finish();
bool nextResult();
//将私有的东西都放在QSqlQueryPrivate里面，给用户调用的都是共有的
private:
QSqlQueryPrivate* d;
};
QT_END_NAMESPACE
QT_END_HEADER
#endif // QSQLQUERY_H
