Programming Oracle® Triggers and Stored Procedures, Third Edition

11.6. String Concatenation

The concatenation operator is:

||

This operator concatenates strings, but you can concatenate other types. PL/SQL does implicit conversion, such as converting a number and date type variable to a string. This enables statements to concatenate various types, but only if the concatenated item converts to a string.

DECLARE
    professor_name VARCHAR2(100) := 'Professor Smith';
    hire_date      DATE          := SYSDATE;
    dalary         NUMBER(7,2)   := 10100.50;
    str            VARCHAR2(2000);
BEGIN
    str := professor_name|| ' was hired on '||
           hire_date ||' with a salary of '||
           salary||' per month. ';
    dbms_output.put_line(str);
END;

You precede each single quote that is part of the string with a quote. For example, your string needs to include a single quote because ...