Introduction to SQL

S.Q.L: Sequel

• Supported by all major commercial database systems
• Standardized( SQL2, SQL3…)
• Interaction, Embedded in programs
• Declarative language, based on relational algebra

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DDL: Data Definition Language
create, drop…

DML: Data Manipulation Language
select,insert,delete,update…

Other Commands
indexs, constraints…

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3. Select A1, A2, ..., An   What to return1. From R1, R2, ..., Rm     Relations2. Where condition          Combination of Filter 

Equivalent:

ΠA1,A2,...,An(σcondition(R1×R2,...,Rn))

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