SQL overview

ReferenceApplies to: Unified engine deployments

Unified accepts Spark-style SQL with documented engine and connector restrictions. The same language is available through Workbench, SQL notebook cells, and live reference examples. Familiar syntax from another SQL system does not establish compatibility by itself.

Statement structure

Submit a single statement or use an example script that submits its statements in order. A semicolon terminates a statement. String literals, quoted identifiers, and comments can contain semicolons without separating statements.

Element	Form	Meaning
Identifier	`item`, `i_item_sk`	An object or column name
Quoted identifier	`item-key`	An identifier containing punctuation or a reserved word
Qualified table	`catalog.namespace.table`	Explicit data location
String literal	`'Books'`	Text; escape an apostrophe by doubling it
Line comment	`-- explanation`	Comment through end of line
Block comment	`/* explanation */`	Comment between delimiters
Alias	`expression AS name`	Output name or source abbreviation

SELECT i_item_sk AS item_key,
       i_item_id AS item_code,
       'It''s SQL' AS description
FROM demo.tpcds.item
ORDER BY i_item_sk
LIMIT 5;

Names and context

A session has a current catalog and namespace. An unqualified table uses that context; a fully qualified name names the destination explicitly. Table aliases shorten column references and resolve ambiguous names in joins. Function names and aliases are matched without ASCII case sensitivity. The session setting spark.sql.caseSensitive controls supported identifier matching.

USE CATALOG demo;
USE tpcds;
SELECT i_item_sk, i_category FROM item ORDER BY i_item_sk LIMIT 5;

Results and table changes

A SELECT returns rows. Metadata commands return descriptions or status. Writes and maintenance can compute or prepare output before their table commit is confirmed. Inspect the operation’s execution and write outcome rather than treating acceptance as completion.

Reference notation

Syntax forms in prose use square brackets for optional parts and descriptive names such as expression or table_name. Runnable SQL blocks use demo.tpcds for sample tables and demo.examples for the write lab. Replace these names with your catalog and namespace.

Area	Continue
SELECT and clauses	Queries
Data types, casts, and expressions	Types and expressions
Functions, signatures, and aliases	Functions
DDL and commands	Statements

Transformation Engine

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Statement structure

Names and context

Results and table changes

Reference notation

​Statement structure

​Names and context

​Results and table changes

​Reference notation

Statement structure

Names and context

Results and table changes

Reference notation