Q41. How to select FirstName from Customers?
To retrieve only the `FirstName` column from the `Customers` table, use the standard `SELECT` projection statement: ```sql SELECT FirstName FROM Customers; ``` ### Perfor...
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Q42. What does the FROM clause do?
The **`FROM`** clause identifies the source table(s), views, joined tables, or subqueries from which data is to be retrieved, filtered, and aggregated. ### Logical SQL Pr...
Q43. Which statement returns only different values?
`SELECT DISTINCT`. It operates on the *entire selected row*. ```sql -- Returns unique city-state combinations SELECT DISTINCT city, state FROM addresses; ```
Q44. Display distinct cities in ADDRESSES(id, street_name, number, city, state)?
To retrieve a list of unique cities without duplicates from the `ADDRESSES` table, use the **`DISTINCT`** keyword: ```sql SELECT DISTINCT city FROM addresses ORDER BY cit...
Q45. Select all records where FirstName is "John"?
To retrieve all columns for records where `FirstName` equals 'John', combine `SELECT *` with a `WHERE` equality filter: ```sql SELECT * FROM Customers WHERE FirstName = '...
Q46. OR vs AND?
`AND` requires ALL conditions to be true. `OR` requires ANY to be true. Use parentheses to control precedence — `AND` binds tighter than `OR`. ```sql -- Without parenthes...
Q47. Which comparison operators exist?
Relational SQL engines provide a rich set of comparison operators evaluated in `WHERE` and `HAVING` clauses: | Operator | Meaning | Example | | :--- | :--- | :--- | | `=`...
Q48. Select records where FirstName="John" AND LastName="Jackson"?
To retrieve records that satisfy multiple simultaneous criteria, use the **`AND`** logical conjunction operator: ```sql SELECT * FROM Customers WHERE FirstName = 'John' A...
Q49. How to select 10 random rows?
```sql -- MySQL SELECT * FROM tbl ORDER BY RAND() LIMIT 10; -- PostgreSQL SELECT * FROM tbl ORDER BY RANDOM() LIMIT 10; -- SQL Server SELECT TOP 10 * FROM tbl ORDER BY NE...
Q50. What does ISNULL(price, 50) return if price is NULL?
If `price` is `NULL`, `ISNULL(price, 50)` evaluates to **`50`**. ### Function Nuances Across Databases: 1. **SQL Server**: `ISNULL(check_expression, replacement_value)` r...