Oracle SQL

Select a column that has the same value in every row of a group without adding it to GROUP BY or wrapping it in MAX, and avoid ORA-00979.

Compute several counts and totals over different subsets of rows in one query with FILTER (WHERE ...), instead of CASE inside aggregates.

Find the largest value, latest date, or worst delay in each group with MAX, and learn when GREATEST is the function you need.

Find the smallest number, the earliest date, or the first name alphabetically in each group with MIN, and get other columns of that row.

Average the values of each group with AVG, understand how NULLs change the divisor, and average intervals in Oracle AI Database 26ai.

Add up values per group with SUM, total intervals of time in Oracle AI Database 26ai, and handle NULLs and empty groups correctly.

Learn the difference between COUNT(*), COUNT(column), and COUNT(DISTINCT), and how to count matches correctly after an outer join.

Store TRUE and FALSE in BOOLEAN columns, select conditions as values, and group, sort, and test BOOLEAN data safely with IS TRUE.

Turn values and objects into XML documents with Oracle's SYS_XMLGEN, rename them with XMLFormat, and aggregate them with SYS_XMLAGG.

Compare two XML documents, list the changed nodes as xdiff operations, and rebuild the new version from the old one with XMLPATCH.

Apply XSLT stylesheets to XML inside the database with XMLTRANSFORM, turning table data into HTML, text, or another XML layout.

Convert XML to indented or compact text of the type you need with XMLSERIALIZE, and parse text into XMLType documents or fragments.

Convert XML query results into SQL numbers, dates, and strings with XMLCAST, and avoid the trap of paths that match several nodes.

Test whether an XML document contains an element or value, and filter rows in WHERE by the content of their XML with bound variables.

Run XQuery paths, functions, and FLWOR expressions against XML inside SQL with XMLQUERY, and turn results into values or text.

Shred XML documents into relational rows and typed columns with XMLTABLE, including attributes, row numbers, and namespaced XML.

Join XML values into one fragment with XMLCONCAT, and create comments, processing instructions, and CDATA sections in SQL.

Aggregate the rows of each group into ordered XML child elements, and nest XMLAGG calls to build a complete document in one query.