说明

简单通过几个小例子展示使用普通SQL操作数据库、绑定变量法操作数据库的语法区别

本文只是展示绑定变量的语法，还有更多值得研究的：

Oracle和SQL Server绑定变量的异同

绑定变量相比于普通SQL的优势

绑定变量在数据库底层的运行原理

普通SQL在数据库底层的运行原理

等等

参考文章

基础数据准备

在Oracle中创建用于测试的数据表，并插入2条测试数据

create table practice(uno varchar(8), uname varchar(20));

insert into practice values('no1', 'name1');

insert into practice values('no2', 'name2');

Delphi执行普通SQL查询

var

AdoConn: TADOConnection;

AdoQry: TADOQuery;

sSql, name, ConStr: string;

begin

sSql := 'select uname from practice where uno = ''no1'' ';

ConStr := 'Provider=OraOLEDB.Oracle.1;Persist Security Info=False;User ID=trade;Password=trade;Data Source=MINE' ;

AdoConn := TADOConnection.Create(nil);

AdoQry := TADOQuery.Create(nil);

try

try

AdoConn.ConnectionString := ConStr;

AdoConn.Open;

AdoQry.Connection := AdoConn;

AdoQry.SQL.Text := sSql;

//AdoQry.ExecSQL; //普通SQL查询的时候如果使用ExecSQL会报错

AdoQry.Open;

name := AdoQry.FieldByName('uname').AsString;

ShowMessage(name);

except

ShowMessage('普通SQL查询报错');

end;

finally

AdoQry.Free;

AdoConn.Free;

end;

end;

Delphi绑定变量查询

var

AdoConn: TADOConnection;

AdoQry: TADOQuery;

sSql, name, ConStr: string;

begin

sSql := 'select uname from practice where uno = :no';

ConStr := 'Provider=OraOLEDB.Oracle.1;Persist Security Info=False;User ID=trade;Password=trade;Data Source=MINE' ;

AdoConn := TADOConnection.Create(nil);

AdoQry := TADOQuery.Create(nil);

try

try

AdoConn.ConnectionString := ConStr;

AdoConn.Open;

AdoQry.Connection := AdoConn;

AdoQry.SQL.Text := sSql;

AdoQry.Parameters.ParamByName('no').Value:= 'no2';

//AdoQry.ExecSQL; //绑定变量法更新时使用ExecSQL会报错

AdoQry.Open;

name := AdoQry.FieldByName('uname').AsString;

ShowMessage(name);

except

ShowMessage('绑定变量法查询报错');

end;

finally

AdoQry.Free;

AdoConn.Free;

end;

end;

Delphi普通SQL更新

var

AdoConn: TADOConnection;

AdoQry: TADOQuery;

sSql, ConStr: string;

begin

sSql := 'update practice set uname = ''testnm'' WHERE uno = ''no1'' ';

ConStr := 'Provider=OraOLEDB.Oracle.1;Persist Security Info=False;User ID=trade;Password=trade;Data Source=MINE' ;

AdoConn := TADOConnection.Create(nil);

AdoQry := TADOQuery.Create(nil);

try

try

AdoConn.ConnectionString := ConStr;

AdoConn.Open;

AdoQry.Connection := AdoConn;

AdoQry.SQL.Text := sSql;

AdoQry.ExecSQL;

except

ShowMessage('普通SQL更新报错');

end;

finally

AdoQry.Free;

AdoConn.Free;

end;

end;

Delphi绑定变量更新

var

AdoConn: TADOConnection;

AdoQry: TADOQuery;

sSql, ConStr: string;

begin

sSql := 'update practice '

+ set uname = case when :name_condition1 = ''condition'' then :name_result1 else :name_result2 end '

+ 'where uno = :no_condition1';

//如果是下面这样的，SQL中有; 那么就会导致执行报错：ORA-00911: 无效字符

//sSql := 'update practice '

// + 'set uname = case when :name_condition1 = ''condition'' then :name_result1 else :name_result2 end '

// + 'where uno = :no_condition1;';

ConStr := 'Provider=OraOLEDB.Oracle.1;Persist Security Info=False;User ID=trade;Password=trade;Data Source=MINE' ;

AdoConn := TADOConnection.Create(nil);

AdoQry := TADOQuery.Create(nil);

try

try

AdoConn.ConnectionString := ConStr;

AdoConn.Open;

AdoQry.Connection := AdoConn;

AdoQry.SQL.Text := sSql;

AdoQry.Parameters.ParamByName('name_condition1').Value:= 'condition';

AdoQry.Parameters.ParamByName('name_result1').Value:= 'result1';

AdoQry.Parameters.ParamByName('name_result2').Value:= 'result2';

AdoQry.Parameters.ParamByName('no_condition1').Value:= 'filter';

//实现对practice表中uno='filter'的记录进行有条件的更新

//AdoQry.Open; //绑定变量法更新时使用Open会报错

AdoQry.ExecSQL; //应该使用ExecSQL

except

ShowMessage('绑定变量法更新报错');

end;

finally

AdoQry.Free;

AdoConn.Free;

end;

end;

【特别小心】如果使用绑定变量法的两个变量同名的话，会导致报错：“不正常的定义参数对象，提供了不一致或不完整的信息”，比如下面例程所展示的

var

AdoConn: TADOConnection;

AdoQry: TADOQuery;

sSql, ConStr: string;

begin

sSql := 'update practice set uname = :name where uname = :name'; //两个变量同名，都是:name，会导致报错

ConStr := 'Provider=OraOLEDB.Oracle.1;Persist Security Info=False;User ID=trade;Password=trade;Data Source=MINE' ;

AdoConn := TADOConnection.Create(nil);

AdoQry := TADOQuery.Create(nil);

try

try

AdoConn.ConnectionString := ConStr;

AdoConn.Open;

AdoQry.Connection := AdoConn;

AdoQry.SQL.Text := sSql;

AdoQry.Parameters.ParamByName('name').Value:= 'name1';

//AdoQry.Open; //绑定变量法更新时使用Open会报错

AdoQry.ExecSQL; //应该使用ExecSQL

except

ShowMessage('绑定变量法更新报错');

end;

finally

AdoQry.Free;

AdoConn.Free;

end;

end;

Delphi执行普通SQL插入

var

AdoConn: TADOConnection;

AdoQry: TADOQuery;

sSql, name, ConStr: string;

begin

sSql := 'insert into practice(uno, uname) values(''no4'', ''name4'')';

ConStr := 'Provider=OraOLEDB.Oracle.1;Persist Security Info=False;User ID=trade;Password=trade;Data Source=MINE' ;

AdoConn := TADOConnection.Create(nil);

AdoQry := TADOQuery.Create(nil);

try

try

AdoConn.ConnectionString := ConStr;

AdoConn.Open;

AdoQry.Connection := AdoConn;

AdoQry.SQL.Text := sSql;

AdoQry.ExecSQL;

//AdoQry.Open; //普通SQL插入新数据时使用Open会报错

except

ShowMessage('普通SQL插入报错');

end;

finally

AdoQry.Free;

AdoConn.Free;

end;

end;

Delphi绑定变量插入

var

AdoConn: TADOConnection;

AdoQry: TADOQuery;

sSql, name, ConStr: string;

begin

sSql := 'insert into practice(uno, uname) values(:no, :name)';

ConStr := 'Provider=OraOLEDB.Oracle.1;Persist Security Info=False;User ID=trade;Password=trade;Data Source=MINE' ;

AdoConn := TADOConnection.Create(nil);

AdoQry := TADOQuery.Create(nil);

try

try

AdoConn.ConnectionString := ConStr;

AdoConn.Open;

AdoQry.Connection := AdoConn;

AdoQry.SQL.Text := sSql;

AdoQry.Parameters.ParamByName('no').Value:= 'no3';

AdoQry.Parameters.ParamByName('name').Value:= 'name3';

AdoQry.ExecSQL;

//AdoQry.Open; //绑定变量法插入新数据时使用Open会报错

except

ShowMessage('绑定变量法插入报错');

end;

finally

AdoQry.Free;

AdoConn.Free;

end;

end;