März Das komplette SQL Tutorial gibt es auch als kostenloses PDF zum download. . Mit dem SELECT Befehl kann man Daten aus der Datenbank. Our tutorial will start with the basics of SQL, such as how to retrieve and manipulate data. Then we will move to the more advanced topics such as how to create. SQLite understands most of the standard SQL language. But it does omit some features while at the same time adding a few features of its own. This document.
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However, if you divide a number by null, the result is a null or unknown.
In the example on the slide, the EMP table actually contains fourteen rows but there befehls only three unique department numbers in the table. A null value represents that fact. Literal Character Strings continued The example on the slide displays names and jobs of all employees.
SQL statements can be entered on one or many lines. Character and date column headings can be truncated, but number headings cannot be truncated. Operator Precedence continued The example on the slide displays the name, salary, and annual compensation of employees.
Query Language Understood by SQLite
Fill in username, password, and database. Number headings and data are right-justified.
The example on the slide displays all the department numbers and locations from the DEPT table. To illustrate viewing a query containing no parentheses and executing a query with parentheses to override rules of precedence. Oracle SQL contains many extensions.
You can use parentheses to force the expression within parentheses to be evaluated first. In the following example, the name and salary for each employee is concatenated with a literal to give the returned rows more meaning.
As mentioned in the last slide, column headings appear in uppercase by default. Throughout this course, the words keyword, clause, and statement are used. Also show that the aliases always appear in uppercase, unless enclosed within double quotation marks.
You then see the SQL prompt. Column aliases are covered later in this lesson. The column has the heading Employee Details. If operators within an expression are of same priority, then evaluation is done from left to right.
Keywords typically are entered in uppercase; all other words, such as table names and columns, are entered in lowercase. The spaces improve the readability of the output. Notice that the employee number and job are combined to make a single output column.
Questions 2—4 are paper-based. Practices zql intended to introduce all topics covered in the lesson. You may need to restrict the columns that are displayed.
Einfache SQL-Befehle Schedule: Timing Topic 40 minutes Lecture
Take the practice slowly and precisely. FROM bestimmt welche Tabelle. To illustrate the use of aliases in expressions. The example on the slide displays all the department numbers from the EMP table. Instead, enter only your username.
Alle wichtigen SQL-Befehle
Because the COMM column in the arithmetic expression is null, the result is null. To log in through a Windows environment: Columns on either side of the operator are combined to make a single output column. A statement is a combination of two or more clauses.