Page 281 - PYTHON-12

Table: boys Table: girls

Rollno Name Rollno Name
1 Rohan 6 Reema
12 Jayant 10 Jaya
3 Tinku

mysql> SELECT Name FROM boys WHERE

Rollno < 12 UNION
SELECT Name FROM girls WHERE Rollno > 6;
The resultant table is:
Name
Rohan
Tinku
Jaya

mysql> SELECT Rollno,
Name FROM boys

UNION
SELECT Rollno, Name FROM girls ORDER BY girls.name;
The resultant table is:
Rollno Name
10 Jaya
12 Jayant
6 Reema
1 Rohan
3 Tinku

MEMORY BYTES
 SQL is a language that is used to create, modify and access a database.
 The various processing capabilities of SQL are Data Definition Language (DDL), Data Manipulation Language (DML)
and Data Control Language (DCL).
 DDL is used to create and delete tables, views or indexes.
 DML is used to modify and update the database.
 DESCRIBE or DESC is used to show the structure of a table.
 The SELECT statement is used to fetch data from one or more database tables.
 SELECT * means display all columns.

 The WHERE clause is used to select specific rows.
 The DESCRIBE statement is used to see the structure of a table.
 We can change the structure of a table, i.e., add, remove or change its column(s) using the ALTER TABLE statement.
 The keyword DISTINCT is used to eliminate redundant data from display. Relational Database and SQL
 Logical operators OR and AND are used to connect relational expressions in WHERE clause.
 Logical operator NOT is used to negate a condition.

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