Create Tables and Choose Column Types

What you will be able to do

• Distinguish table definition from column type in a realistic create tables and choose column types case.
• Interpret the database evidence and boundary associated with primary key.
• Choose an appropriate action involving column constraint without exceeding the named data scope.
• Verify schema inspection through an observable database result and reproducible handoff.

01

Frame Create Tables and Choose Column Types

Translate a small data model into PostgreSQL tables with meaningful column names, suitable types, stable keys, and enforceable constraints.

A repair shop needs a devices table for asset tags, model names, purchase dates, and replacement values. The schema must reject missing identity and preserve values in useful technical forms.

Keep the database target, stored state, input values, expected result, and allowed change scope separate. Begin in an isolated practice database, inspect before modifying, and preserve enough evidence to repeat the decision.

02

Table definition

CREATE TABLE defines a named relation and its columns. Within create tables and choose column types, this concept answers a separate data question and retains its own observable evidence.

Name the row subject before declaring the table and its fields. Apply that action to the named database case before broadening the query or changing more stored state.

Respect this boundary: do not combine unrelated customers, repairs, and devices in one row. The required result is specific: each accepted row represents one device consistently.

03

Column type

A column type limits the form of values stored in that field. Within create tables and choose column types, this concept answers a separate data question and retains its own observable evidence.

Choose date, numeric, text, or other types from the field's meaning. Apply that action to the named database case before broadening the query or changing more stored state.

Respect this boundary: do not choose text merely because it accepts many inputs. The required result is specific: stored values support the comparisons and operations they require.

04

Primary key

A primary key gives each table row a unique non-null identity. Within create tables and choose column types, this concept answers a separate data question and retains its own observable evidence.

Declare a stable device identifier as the table's primary key. Apply that action to the named database case before broadening the query or changing more stored state.

Respect this boundary: do not use a mutable model name as row identity. The required result is specific: duplicate or missing device identifiers are rejected.

05

Column constraint

Column and table constraints enforce rules beyond basic data types. Within create tables and choose column types, this concept answers a separate data question and retains its own observable evidence.

Apply NOT NULL, UNIQUE, or CHECK where the business rule requires it. Apply that action to the named database case before broadening the query or changing more stored state.

Respect this boundary: do not encode a critical rule only in a comment. The required result is specific: invalid device rows fail at the shared database boundary.

06

Schema inspection

Schema inspection confirms the database stored the intended definition. Within create tables and choose column types, this concept answers a separate data question and retains its own observable evidence.

Inspect the created table and compare each column with the model. Apply that action to the named database case before broadening the query or changing more stored state.

Respect this boundary: do not infer the schema from a single successful insert. The required result is specific: the declared names, types, keys, and constraints match the design.

07

Apply Create Tables and Choose Column Types to One Case

Use the case as a bounded database task: A repair shop needs a devices table for asset tags, model names, purchase dates, and replacement values. The schema must reject missing identity and preserve values in useful technical forms.

First, name the row subject before declaring the table and its fields. Then, choose date, numeric, text, or other types from the field's meaning. Keep both observations with the target database and expected result before choosing the next statement.

Next, declare a stable device identifier as the table's primary key. After that, apply not null, unique, or check where the business rule requires it. Finish only after you inspect the created table and compare each column with the model.

08

Recap Before Practice and Prove

Table definition: CREATE TABLE defines a named relation and its columns. In the database case, name the row subject before declaring the table and its fields. Preserve the boundary: do not combine unrelated customers, repairs, and devices in one row.

Column type: A column type limits the form of values stored in that field. In the database case, choose date, numeric, text, or other types from the field's meaning. Preserve the boundary: do not choose text merely because it accepts many inputs.

Primary key: A primary key gives each table row a unique non-null identity. In the database case, declare a stable device identifier as the table's primary key. Preserve the boundary: do not use a mutable model name as row identity.

Column constraint: Column and table constraints enforce rules beyond basic data types. In the database case, apply not null, unique, or check where the business rule requires it. Preserve the boundary: do not encode a critical rule only in a comment.

Schema inspection: Schema inspection confirms the database stored the intended definition. In the database case, inspect the created table and compare each column with the model. Preserve the boundary: do not infer the schema from a single successful insert.