How to call mysql data in java

Java method of calling mysql data: first define a process to obtain the total number of records in the users table, and set 10 to the variable count; then modify the result character of the mysql statement; then overwrite the result to the variable a; finally Display the value of variable a.

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Java method of calling mysql data:

Process

Define a process to obtain the total number of records in the users table and set 10 to the variable count

create procedure simpleproc(out count int)
begin
    select count(id) into count from users;
end

Modify the result symbol of the mysql statement to;

mysql &gt ; delimiter ;

Call the procedure and return the result to variable a, @ is the symbol that defines the variable

call simpleproc(@a);

Display the value of variable a

select @a;

The following is the process of calling Mysql from Java

String sql = "{call simpleproc(?)}";
Connection conn = JdbcUtil.getConnection();
CallableStatement cstmt = conn.prepareCall(sql);
cstmt.registerOutParameter(1,Types.INTEGER);
cstmt.execute();
Integer count = cstmt.getInt(1);
System.out.println("共有" + count + "人");

Function

Modify the result character of the mysql statement to

mysql > delimiter

Define a function to complete string splicing

create function hello( s char(20) ) returns char(50) 
return concat('hello，',s,'!');

Modify the result symbol of the mysql statement to;

##mysql > delimiter;

Call function

select hello('world');

The following is the function that Java calls Mysql

String sql = "{? = call hello(?)}";
Connection conn = JdbcUtil.getConnection();
CallableStatement cstmt = conn.prepareCall(sql);
cstmt.registerOutParameter(1,Types.VARCHAR);
cstmt.setString(2,"zhaojun");
cstmt.execute();
String value = cstmt.getString(1);
System.out.println(value);
JdbcUtil.close(cstmt);
JdbcUtil.close(conn);

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