SQL query Statement splicing tips (master do not spray)

1. The basic query statement is followed by a WHERE 1=1 to facilitate the query condition.

ASKSTR: = ' select * from twork where 1=1 ', if Length (Cxteworkid.text) <> 0 Then Beginaskstr: = Askstr + ' and Gworki D like ' +quotedstr ('% ' + cxteworkid.text + '% ') end;

　　

2. Multiple-table queries can replace a table with a single string. Logically clearer.

worktable = ' Select Gworkid from twork where 1=1 '; paytable = ' select sum (gxmtotal) as Sgxmtotal,gxmtype from Tpay where Gworkid in '; Paygroupby = ' Group by Gxmtype ';

ASKSTR: = paytable + ' (' + worktable + tmpwhere + ') ' + paygroupby;

3. Define a connection function to determine if the initialization of the database is successful and easy to control.

function Tdm.initdbok:boolean;begin  Result: = true;  If FileExists (dbfilename) then  begin    Fdconn.drivername: = ' SQLite ';    Fdconn.loginprompt: = false;    FDConn.Params.Clear;    fdconn.params.values[' Database ': = Dbfilename;    fdconn.params.values[' DriverID ': = ' SQLite ';    fdconn.params.values[' CharacterSet ': = ' utf8 ';    Try      fdconn.connected: = true;    Except      result: = false;    End;  End  Else    result: = False;end;

　　

SQL query Statement splicing tips (master do not spray)