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Structured Query Language, or SQL, is the lifeblood of data management and handling in modern technology. Through SQL queries, we can communicate with databases, allowing us to fetch, insert, delete, and manipulate data to drive insights and applications. This blog post aims to provide beginners with essential information and examples on how to construct SQL queries effectively.
The SELECT Statement
At the core of SQL is the SELECT statement. We use it to select data from a database. The data returned is stored in a ‘result-table’. Usage:
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SELECT column1, column2, ... FROM table_name; |
To select all columns from a table, use the wildcard character *
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SELECT * FROM table_name; |
The WHERE Clause
The WHERE clause is used to filter records. It is used in combination with logical operators such as =, <>, >, <, etc. Example:
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SELECT column1, column2 FROM table_name WHERE condition; |
The INSERT INTO Statement
To insert new data into a database, we use the INSERT INTO statement. Usage:
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INSERT INTO table_name (column1, column2, column3, ...) VALUES (value1, value2, value3, ...); |
The UPDATE Statement
Existing records become out-of-date? Worry not. The UPDATE statement is here to rescue. Here’s how to use it:
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UPDATE table_name SET column1 = value1, column2 = value2, ... WHERE condition; |
The DELETE Statement
And when data is no longer necessary, we have the DELETE statement to permanently remove data. But use with caution! Here is how:
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DELETE FROM table_name WHERE condition; |
Final Note
Keep in mind, all SQL commands are not case-sensitive: It could be written in uppercase or lowercase – it will function the same. Practice makes perfect, so try these basics out on your data. Happy Querying!