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The Query Compiler

The Query Compiler. Varun Sud ID: 104. Agenda. Parsing Syntax analysis and Parse Trees. Grammar for a simple subset of SQL Base Syntactic Categories The Preprocessor. Parsing. Three steps of query processor Parse SQL query into parse tree. Transform parse tree into expression tree.

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The Query Compiler

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  1. The Query Compiler Varun Sud ID: 104

  2. Agenda • Parsing • Syntax analysis and Parse Trees. • Grammar for a simple subset of SQL • Base Syntactic Categories • The Preprocessor.

  3. Parsing • Three steps of query processor • Parse SQL query into parse tree. • Transform parse tree into expression tree. • Transform logical query plan into physical query plan.

  4. Syntax analysis and parse trees • Parser converts SQL text to parse tree • Nodes of trees correspond to: • Atoms: lexical elements such as keywords, names of attributes or relations etc • Syntactic categories, which are names of families of query subparts.

  5. Grammar for simple subset of SQL • Queries • <Query> ::= <SFW> • <Query> ::= (<Query>) • SFW: select from were • ::= means “can be expressed as.”

  6. Contd. • Select-From-Where Forms • <SFW> ::= SELECT <SelList> FROM <FromList> WHERE <Condition> • Select-Lists • <SelList> ::= <Attribute> ,<SelList> • <SelList> ::= <Attribute>

  7. Contd. • Conditions • <Condition> ::= <Condition> AND <Condition> • <Condition> ::= <Tuple> IN <Query> • <Condition> ::= <Attribute> = <Attribute> • <Condition> ::= <Attribute> LIKE <Pattern> • <Tuple> ::= <Attribute>

  8. The Preprocessor • Preprocessor is responsible for semantic checking. • Preprocessor must: • Check relation uses. • Check and resolve attribute uses • Check types.

  9. Thank You

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