======================================= Using additional DTML tags in SQLScript ======================================= Inserting optional tests with 'sqlgroup' ---------------------------------------- It is sometimes useful to make inputs to an SQL statement optinal. Doing so can be difficult, because not only must the test be inserted conditionally, but SQL boolean operators may or may not need to be inserted depending on whether other, possibly optional, comparisons have been done. The 'sqlgroup' tag automates the conditional insertion of boolean operators. The 'sqlgroup' tag is a block tag that has no attributes. It can have any number of 'and' and 'or' continuation tags. Suppose we want to find all people with a given first or nick name and optionally constrain the search by city and minimum and maximum age. Suppose we want all inputs to be optional. We can use DTML source like the following::

age >=

age <=

This example illustrates how groups can be nested to control boolean evaluation order. It also illustrates that the grouping facility can also be used with other DTML tags like 'if' tags. The 'sqlgroup' tag checks to see if text to be inserted contains other than whitespace characters. If it does, then it is inserted with the appropriate boolean operator, as indicated by use of an 'and' or 'or' tag, otherwise, no text is inserted. Inserting optional tests with 'sqlgroup' ---------------------------------------- It is sometimes useful to make inputs to an SQL statement optinal. Doing so can be difficult, because not only must the test be inserted conditionally, but SQL boolean operators may or may not need to be inserted depending on whether other, possibly optional, comparisons have been done. The 'sqlgroup' tag automates the conditional insertion of boolean operators. The 'sqlgroup' tag is a block tag. It can have any number of 'and' and 'or' continuation tags. The 'sqlgroup' tag has an optional attribure, 'required' to specify groups that must include at least one test. This is useful when you want to make sure that a query is qualified, but want to be very flexible about how it is qualified. Suppose we want to find people with a given first or nick name, city or minimum and maximum age. Suppose we want all inputs to be optional, but want to require *some* input. We can use DTML source like the following::

age >=

age <=

This example illustrates how groups can be nested to control boolean evaluation order. It also illustrates that the grouping facility can also be used with other DTML tags like 'if' tags. The 'sqlgroup' tag checks to see if text to be inserted contains other than whitespace characters. If it does, then it is inserted with the appropriate boolean operator, as indicated by use of an 'and' or 'or' tag, otherwise, no text is inserted. Inserting values with the 'sqlvar' tag -------------------------------------- The 'sqlvar' tag is used to type-safely insert values into SQL text. The 'sqlvar' tag is similar to the 'var' tag, except that it replaces text formatting parameters with SQL type information. The sqlvar tag has the following attributes: `name` The name of the variable to insert. As with other DTML tags, the 'name=' prefix may be, and usually is, ommitted. `type` The data type of the value to be inserted. This attribute is required and may be one of 'string', 'int', 'float', or 'nb'. The 'nb' data type indicates a string that must have a length that is greater than 0. `optional` A flag indicating that a value is optional. If a value is optional and is not provided (or is blank when a non-blank value is expected), then the string 'null' is inserted. For example, given the tag:: if the value of 'x' is:: Let\'s do it then the text inserted is: 'Let''s do it' however, if x is ommitted or an empty string, then the value inserted is 'null'.