Reference of the median value in a Delphi SQL statement

1. directly use the value (number or string)

Number: Select * from CC where no = 5; or select * from CC where no = '5'

String: Select * from CC where name = 'dashan'

 

2. Use Variables

VaR

XX: string;

SQL: widestring;

.........

If the variable XX is a numeric string, both statements can

SQL: = 'select * from CC where no = '+ xx; or

SQL: = 'select * from CC where no = ''' + xx + '''; (string variables must be enclosed by single quotes)

Non-pure numeric string

SQL: = 'select * from CC where no = ''' + xx + '''; (string variables must be enclosed by single quotes)

 

3. Use Parameters

VaR

QQ: string;

......

Self. adocommand1.commandtext: = 'insert into Ceshi (SS) values (: XX) '; // The parameter XX used here
Self. adocommand1.parameters. paramvalues ['xx']: = QQ; // assign a value to the parameter

Note that the order in which parameters are used: first use parameters (define SQL statements with parameters), and then define the value of parameters.