DML is a group of commands in SQL that allows you to modify data in the database, while DDL is a group of commands that allows you to create and drop database tables. Learn about the differences between DML and DDL commands and see examples of both.
- [Instructor] So far in our course we wrote and executed SQL queries which essentially allows us to retrieve data from database tables. For example, select * from employees will return all columns and all rows from the employees tables. However, in addition to SQL queries, two additional categories of statements that are part of the SQL language are DML and DDL commands. Let's understand what DML and DDL command mean.
So DML, which stands for Data Modification Language, is used to modify existing data in your database. For example, you can use DML commands to insert data into our tables such as using an insert command, specifying the table name, column names and the values which we would like to insert into our table. We can also use DML commands to update existing data, as well as delete rows.
We will see all of these examples throughout this chapter. We also have another category of commands known as DDL commands, or Data Definition Language, which are used to create new database objects. So for example, we can create a new table using the DDL create table command, specifying the table name, and the column names, as well as the data types for each column. So to recap, we run SQL queries when we wish to retrieve data from our database tables.
We run DML or Data Modification Language commands when we wish to modify the data in our database such as inserting new records, updating existing values, or deleting rows and we run DDL commands, or Data Definition Language commands, when we want to create new database objects, such as creating new database tables.
Author
Released
1/17/2018Note: This training course is appropriate for beginning database developers with no prior experience with SQL or Oracle.
- Using Oracle SQL*Developer, the free development environment
- Selecting data from tables
- Filtering data
- Using functions to manipulate data
- Joining data from tables
- Creating tables
- Updating values
- Truncating data
- Grouping and ordering result sets
- Working with primary keys
- Checking constraints
Skill Level Beginner
Duration
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Introduction
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Welcome1m 37s
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1. Introduction to SQL
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What is SQL?2m 30s
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Database tables2m 21s
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Overview of table data types4m 21s
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SQL query structure4m 38s
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2. Preparing the Course Environment
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Downloading the course VM2m 16s
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3. Using Oracle SQL Developer
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Exploring database objects1m 29s
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Filtering specific objects1m 25s
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Using SQL Developer tabs2m 18s
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Viewing query output1m 18s
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4. Basic SELECT Queries
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Using WHERE to filter dates2m 42s
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Using column aliases2m 18s
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Using ORDER BY3m 29s
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5. String, Number, and Date Functions
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Introduction to functions1m 39s
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Using LENGTH1m 4s
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Using CONCAT4m 48s
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Using LOWER and UPPER2m 44s
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Using INSTR4m 32s
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Using RPAD and LPAD3m 31s
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Using ROUND1m 15s
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Using TRUNC1m 36s
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Using SYSDATE1m 59s
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Using SYSTIMESTAMP1m 37s
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Using MONTHS_BETWEEN3m 2s
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Using ADD_MONTHS1m 17s
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6. Joining Table Data
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Joining data from tables4m 12s
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INNER JOIN1m 17s
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LEFT JOIN2m 55s
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RIGHT JOIN1m 55s
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FULL OUTER JOIN1m 59s
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7. Manipulating Data
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Creating a simple table2m 1s
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COMMIT and ROLLBACK2m 23s
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Introduction to transactions3m 43s
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Deleting rows for a table3m 23s
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Updating values2m 40s
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8. Grouping Data
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Using aggregate functions2m 24s
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Using GROUP BY2m 45s
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Using HAVING3m
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9. Advanced Topics
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Primary keys2m 47s
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NOT NULL constraints1m 36s
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Check constraints3m 2s
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Foreign key constraints6m 4s
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Subqueries4m 39s
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Conclusion
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Next steps1m 33s
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Video: Introduction to DML and DDL commands