Where clause
A WHERE clause is a query-language clause that restricts returned or affected records to those satisfying a specified predicate.
Learn SQL in a Month of Lunches
A WHERE clause is the SQL clause that restricts query results by requiring rows to satisfy one or more conditions.
- How it is used
- Filters query results to rows matching specific criteria and safeguards targeted DELETE operations.
- How deep it goes
- Explains equality filters for numbers and strings, multiple-condition logic, parentheses, ordering, and common syntax or matching mistakes.
- Examples
- Uses title advances, title names, prices, publication dates, royalties, author payment methods, and a targeted title deletion.
- What you can do after
- Apply it via SQL to retrieve or delete only rows that satisfy explicit numeric, string, and combined conditions.
Read how Learn SQL in a Month of Lunches explains where clause →
ScyllaDB in Action
A WHERE clause is a query-language clause that restricts returned or affected rows according to a condition.
- How it is used
- Restricts rows for SELECT, UPDATE, and DELETE operations while guiding efficient partition-aware access.
- How deep it goes
- Explains syntax, key-based targeting, distributed read behavior, SSTable matching, and risks of unrestricted or filtered queries.
- Examples
- Uses restaurant reviews, author bios, article rows, individual cells, and exact primary-key conditions as concrete examples.
- What you can do after
- Apply it via CQL to read, update, or delete deliberately targeted rows and avoid broad distributed operations.
Kafka Streams in Action, Second Edition
A WHERE clause is an SQL query clause that restricts returned records to those satisfying a Boolean condition.
- How it is used
- Refines push and pull query results by retaining rows that satisfy a Boolean condition.
- How deep it goes
- Defines filtering, demonstrates comparisons and key lookup, and names pseudo-columns; stops short of enumerating every condition.
- Examples
- Uses activity leaders, total_steps greater than 1,000, ROWTIME filtering, and a key lookup for Smith.
- What you can do after
- Apply it via ksqlDB to filter continuous updates or point-in-time results by data and record metadata.
Read how Kafka Streams in Action, Second Edition explains where clause →
Logs and Telemetry
A WHERE clause is a query construct that retains records satisfying a predicate over event values.
- How it is used
- Filters event streams before applying selected functions such as count.
- How deep it goes
- Demonstrates predicate syntax and output behavior, but does not detail predicate grammar or evaluation internals.
- Examples
- Uses rand_value > 0 with unix_timestamp() and count(rand_value) over the random-num tag.
- What you can do after
- Apply it in a configured stream query to count only events whose selected value exceeds zero.
Build Python Web Apps with Streamlit
A WHERE clause is a SQL query component that restricts affected or returned rows according to a condition.
- How it is used
- Restricts returned, updated, or deleted database rows according to conditions.
- How deep it goes
- Demonstrates equality, LIKE, AND, and identifier-based filtering without detailing query planning or optimization.
- Examples
- Uses Alice’s fox haiku, haiku identifier 1, and haiku identifier 2 as filtering examples.
- What you can do after
- Apply it via PostgreSQL to retrieve, update, or delete specifically matching rows.
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Grokking Relational Database Design
A WHERE clause is an SQL clause that restricts query results to rows satisfying a predicate.
- How it is used
- Filters rows returned by SELECT from one or more tables.
- How deep it goes
- Explains numeric, string, and combined conditions with AND and OR, but does not descend into advanced filtering behavior.
- Examples
- Uses product names, prices, descriptions, and manufacturers in numeric, string, and combined filtering queries.
- What you can do after
- Apply it via SQL to retrieve only rows matching numeric, string, or combined conditions.
Read how Grokking Relational Database Design explains where clause →
Practical Automation with PowerShell: Effective scripting from the console to the cloud
A where clause is the SQL query clause that restricts returned rows according to conditions on column values.
- How it is used
- Filters SQL data for operational PowerShell queries and reusable server-inventory functions.
- How deep it goes
- Explains filtering, parameterization, injection risks, and dynamic function construction, but does not detail complete SQL condition syntax.
- Examples
- Uses server-name filtering, parameterized Invoke-DbaQuery calls, injection strings, and Get-PoshServer filter combinations.
- What you can do after
- Apply it via Invoke-DbaQuery and reusable PowerShell functions while avoiding unsafe string-built conditions.
Related concepts
- SQLpart of · SQL is a standardized declarative language for defining, querying, and manipulating data and structures in relational database systems.
- filteringused by · Filtering is the operation of selecting or excluding items from data or a collection according to specified criteria.
- having clausecontrasts with · A HAVING clause is a SQL clause that filters groups or aggregate results according to a condition.
- $PSBoundParametersproduced by · $PSBoundParameters is an automatic PowerShell variable containing the parameters supplied to the currently executing command and their values.
- order by clauseuses · An ORDER BY clause specifies the ordering of query results according to one or more expressions, fields, or sort directions.
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