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- SQL Syntax - W3Schools
SQL Statements Most of the actions you need to perform on a database are done with SQL statements SQL statements consist of keywords that are easy to understand The following SQL statement selects all records from the table named "Customers":
- SQL Introduction - W3Schools
SQL is a Standard - BUT Although SQL is an ANSI ISO standard, there are different versions of the SQL language However, to be compliant with the ANSI standard, they all support at least the major commands (such as SELECT, UPDATE, DELETE, INSERT, WHERE) in a similar manner
- SQL LIKE Operator - W3Schools
The SQL LIKE Operator The LIKE operator is used in a WHERE clause to search for a specified pattern within a column's text data There are two wildcards often used in conjunction with the LIKE operator: A percent sign % - represents zero, one, or multiple characters A underscore sign _ - represents a single character The following SQL selects all customers that starts with "a":
- SQL SELECT Statement - W3Schools
The SQL SELECT Statement The SELECT statement is used to select data from a database
- SQL UPDATE Statement - W3Schools
The SQL UPDATE Statement The UPDATE statement is used to update or modify one or more records in a table UPDATE Syntax
- SQL NULL Values - IS NULL and IS NOT NULL - W3Schools
What is a NULL Value? If a field in a table is optional, it is possible to insert or update a record without adding any value to this field This way, the field will be saved with a NULL value A NULL value represents an unknown, missing, or inapplicable data in a database field It is not a value itself, but a placeholder to indicate the absence of data
- SQL WHERE Clause - W3Schools
The SQL WHERE Clause The WHERE clause is used to filter records The WHERE clause is used to extract only those records that fulfill a specific condition
- SQL Constraints - W3Schools
SQL Constraints SQL constraints are rules for data in a table Constraints are used to prevent insertion of invalid data in a table, and ensures the accuracy and reliability of the data in the table If there is any violation between the constraint and the data action, the action is aborted Constraints can be specified in two ways: When a table is created (through the CREATE TABLE statement
- SQL Examples - W3Schools
SQL NULL Values IS NULL Operator IS NOT NULL Operator Examples Explained w 3 s c h o o l s C E R T I F I E D 2 0 2 5 Get Certified! Take the SQL exam and become w3schools certified!!
- SQL GROUP BY Statement - W3Schools
The SQL GROUP BY Statement The GROUP BY statement is used to group rows that have the same values into summary rows, like "Find the number of customers in each country"
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