Documentation Source Text

  }
  delete-stmt-limited {
    stack
        {line DELETE FROM qualified-table-name {optx WHERE expr}}
        {optx
            {stack
              {optx ORDER BY {loop ordering-term ,}}
              {line LIMIT /expression {optx {or OFFSET ,} /expression}}
            }
        }
  }
  detach-stmt {
    line DETACH {optx DATABASE} /database-name
  }
  drop-index-stmt {

             }
          }
  }
  select-stmt {
    stack
       {loop {line select-core nil} {nil compound-operator nil}}
       {optx ORDER BY {loop ordering-term ,}}
       {optx LIMIT /expression {optx {or OFFSET ,} /expression}}
  }
  select-core {
     stack
       {line SELECT {or nil DISTINCT ALL} {loop result-column ,}}
       {optx FROM join-source}
       {optx WHERE expr}
       {optx GROUP BY {loop ordering-term ,} {optx HAVING expr}}

     stack
        {line UPDATE {opt OR {or ROLLBACK ABORT REPLACE FAIL IGNORE}}
              qualified-table-name}
        {line SET {loop {line /column-name = expr} ,} {optx WHERE expr}}
        {optx
            {stack
              {optx ORDER BY {loop ordering-term ,}}
              {line LIMIT /expression {optx {or OFFSET ,} /expression}}
            }
        }
  }
  qualified-table-name {
     line {optx /database-name .} /table-name
          {or nil {line INDEXED BY /index-name} {line NOT INDEXED}}
  }

BubbleDiagram join-op
BubbleDiagram join-constraint
BubbleDiagram ordering-term
BubbleDiagram compound-operator
</tcl>


<p>The SELECT statement is used to query the database.  ^The
result of a SELECT is zero or more rows of data where each row
has a fixed number of columns.  

<p>The SELECT statement is the most complicated command in the SQL language.
To make the description easier to follow, some of the passages below describe
the way the data returned by a SELECT statement is determined as a series of
steps. It is important to keep in mind that this is purely illustrative -

       The set of result rows is computed by aggregating the data according to
       any GROUP BY clause and calculating the result-set expressions for the
       rows of the filtered input dataset.  
  <li> <p>[DISTINCT|DISTINCT/ALL keyword] processing: If the query is a "SELECT
       DISTINCT" query, duplicate rows are removed from the set of result rows.
</ol>

<p>^There are two types of simple SELECT statement - aggregate and 
non-aggregate queries. ^A simple SELECT statement is an aggregate query if
it contains either a GROUP BY clause or one or more aggregate functions
in the result-set. ^Otherwise, if a simple SELECT contains no aggregate
functions or a GROUP BY clause, it is a non-aggregate query.

<p><b>1. Determination of input data (FROM clause processing).</b>
<tcl>hd_fragment fromclause</tcl>