3.2.3
SQL
Structured Query Language
Structured Query Language
A database is a structured collection of data. Structured query language (SQL) is a language used to query this data.
SQL
SQL
- SQL is a language that can tell databases what to do.
- SQL can be used for selecting, inserting, updating, and deleting data.
Select statements
Select statements
- A SELECT statement searches for and returns data. E.g:
- SELECT * FROM table_name;
- The * character tells the database to return all fields.
- The * character can be replaced by specific fields. E.g:
- SELECT name FROM users;
Where clause
Where clause
- Sometimes we don't want to return data for all records.
- We can filter the data using a where clause as follows:
- SELECT * FROM users WHERE ID=3;
- The above line would only return a user's data where they have an ID of 3.
Wildcards
Wildcards
- Sometimes we don't know the exact value we want to use in a where clause.
- We can use wildcards to find records which match some sort of pattern.
- The % symbol can be used to represent anything.
- For example, if we want to find any names starting with 'Ba' then we could query:
- SELECT name FROM users WHERE name LIKE "Ba%";
1Components of a Computer
1.1Structure & Function of the Processor
1.2Types of Processors
2Software & Software Development
2.1Systems Software
2.2Applications Generation
2.3Software Development
3Exchanging Data
3.1Compression, Encryption & Hashing
3.3Networks
4Data Types, Data Structures & Algorithms
4.1Data Types
5Legal, Moral, Cultural & Ethical Issues
5.1Computing Related Legislation
6Elements of Computational Thinking
6.1Thinking Abstractly
6.2Thinking Procedurally
6.3Thinking Logically
7Problem Solving & Programming
7.1Programming Techniques
7.2Programming Construction
Jump to other topics
1Components of a Computer
1.1Structure & Function of the Processor
1.2Types of Processors
2Software & Software Development
2.1Systems Software
2.2Applications Generation
2.3Software Development
3Exchanging Data
3.1Compression, Encryption & Hashing
3.3Networks
4Data Types, Data Structures & Algorithms
4.1Data Types
5Legal, Moral, Cultural & Ethical Issues
5.1Computing Related Legislation
6Elements of Computational Thinking
6.1Thinking Abstractly
6.2Thinking Procedurally
6.3Thinking Logically
7Problem Solving & Programming
7.1Programming Techniques
7.2Programming Construction
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