Laravel DB Query Count

use IlluminateSupportFacadesDB;

// Count rows in a table
$count = DB::table('users')->count();

echo "Number of users: " . $count;

If you're using Eloquent, you can achieve the same result like this:

use AppModelsUser;

// Count rows using Eloquent
$count = User::count();

echo "Number of users: " . $count;

### Adding Conditions
You can also add conditions to the query:

// Query builder with condition
$count = DB::table('users')->where('status', 'active')->count();

// Eloquent with condition
$count = User::where('status', 'active')->count();

This will return the count of rows matching the specified condition.

SELECT DISTINCT column1, column2
FROM table_name;

This query retrieves rows where the combination of `column1` and `column2` values is unique.

### Example
Assume a table `orders` with columns `user_id` and `product_id`:

| user_id | product_id |
|———|————|
| 1 | 101 |
| 2 | 102 |
| 1 | 101 |
| 3 | 103 |

The query:

SELECT DISTINCT user_id, product_id
FROM orders;

Results in:

| user_id | product_id |
|———|————|
| 1 | 101 |
| 2 | 102 |
| 3 | 103 |

### Using Laravel Query Builder
In Laravel, you can achieve the same result with the `distinct` method:

use IlluminateSupportFacadesDB;

$uniqueCombinations = DB::table('orders')
    ->select('user_id', 'product_id')
    ->distinct()
    ->get();

foreach ($uniqueCombinations as $combination) {
    echo "User: {$combination->user_id}, Product: {$combination->product_id}n";
}

This retrieves unique combinations of the two columns from the `orders` table.

### Query Example

SELECT id, competence_id
FROM survey_questions
WHERE id IN (
    SELECT MIN(id)
    FROM survey_questions
    GROUP BY competence_id
)
LIMIT 2;

### Explanation:
1. **Subquery**:
– The subquery groups rows by `competence_id` and selects the minimum `id` for each group (`MIN(id)` ensures you get one `id` per `competence_id`).

2. **Outer Query**:
– Fetches the `id` and `competence_id` for the rows identified by the subquery.

3. **LIMIT**:
– Restricts the result to two unique `competence_id` values with their respective `id`.

### Example Data:
Assume `survey_questions` table:

| id | competence_id |
|—–|—————|
| 1 | 101 |
| 2 | 102 |
| 3 | 101 |
| 4 | 103 |

**Result** for the above query:

| id | competence_id |
|—–|—————|
| 1 | 101 |
| 2 | 102 |

### Using Laravel Query Builder
If you need to do this in Laravel:

use IlluminateSupportFacadesDB;

$results = DB::table('survey_questions')
    ->select('id', 'competence_id')
    ->whereIn('id', function ($query) {
        $query->selectRaw('MIN(id)')
              ->from('survey_questions')
              ->groupBy('competence_id');
    })
    ->limit(2)
    ->get();

foreach ($results as $result) {
    echo "ID: {$result->id}, Competence ID: {$result->competence_id}n";
}

This will produce the same results as the SQL query.

use IlluminateSupportFacadesDB;

$results = DB::table('survey_questions')
    ->select('id', 'competence_id')
    ->whereIn('id', function ($query) {
        $query->selectRaw('MIN(id)')
              ->from('survey_questions')
              ->groupBy('competence_id');
    })
    ->limit(2)
    ->get();

foreach ($results as $result) {
    echo "ID: {$result->id}, Competence ID: {$result->competence_id}n";
}

### Explanation:
1. **`selectRaw`**:
– Used to build the subquery to select the `MIN(id)` for each `competence_id`.

2. **`whereIn`**:
– Ensures the `id` is part of the result from the subquery.

3. **`limit`**:
– Limits the number of rows returned by the outer query.

This query achieves the same logic as your SQL query in a Laravel query builder format.

### SQL Query

SELECT GROUP_CONCAT(id) AS ids
FROM survey_questions
WHERE id IN (
    SELECT MIN(id)
    FROM survey_questions
    WHERE survey_id = 18
    GROUP BY competence_id
)
LIMIT 2;

### Explanation:
1. **`GROUP_CONCAT`**:
– Concatenates all `id` values into a single string, separated by commas.

2. **Subquery**:
– Retrieves the minimum `id` for each `competence_id` where `survey_id = 18`.

3. **`LIMIT`**:
– Ensures the result is restricted to only 2 rows.

### Using Laravel Query Builder
To achieve the same in Laravel, you can use a raw query:

use IlluminateSupportFacadesDB;

$result = DB::table('survey_questions')
    ->selectRaw('GROUP_CONCAT(id) AS ids')
    ->whereIn('id', function ($query) {
        $query->selectRaw('MIN(id)')
              ->from('survey_questions')
              ->where('survey_id', 18)
              ->groupBy('competence_id');
    })
    ->limit(2)
    ->first();

echo "Concatenated IDs: " . $result->ids;

### Output
If the IDs are `1, 2`, the result will be:

Concatenated IDs: 1,2

### SQL Query

SELECT GROUP_CONCAT(id) AS ids
FROM survey_questions
WHERE id IN (
    SELECT MIN(id)
    FROM survey_questions
    WHERE survey_id = 18
    GROUP BY competence_id
);

### Explanation:
1. **Subquery**:
– Groups the rows by `competence_id` and retrieves the `id` of the first occurrence for each group using `MIN(id)`.

2. **`GROUP_CONCAT`**:
– Concatenates the resulting IDs into a single comma-separated string.

3. **Distinct `competence_id`**:
– Handled by grouping in the subquery with `GROUP BY competence_id`.

### Using Laravel Query Builder
In Laravel, you can replicate this using the query builder:

use IlluminateSupportFacadesDB;

$result = DB::table('survey_questions')
    ->selectRaw('GROUP_CONCAT(id) AS ids')
    ->whereIn('id', function ($query) {
        $query->selectRaw('MIN(id)')
              ->from('survey_questions')
              ->where('survey_id', 18)
              ->groupBy('competence_id');
    })
    ->first();

echo "Concatenated IDs: " . $result->ids;

### Example Data
If the `survey_questions` table has the following data:

| id | competence_id | survey_id |
|—–|—————|———–|
| 1 | 101 | 18 |
| 2 | 102 | 18 |
| 3 | 101 | 18 |
| 4 | 103 | 18 |
| 5 | 102 | 19 |

The query will return:

Concatenated IDs: 1,2,4

This ensures that:
– Only rows with `survey_id = 18` are considered.
– Only distinct `competence_id` values are included.
– The IDs are concatenated into a single string.

### SQL Query

SELECT GROUP_CONCAT(id) AS ids
FROM survey_questions
WHERE competence_id IN (
    SELECT DISTINCT competence_id
    FROM survey_questions
    WHERE id IN (
        SELECT MIN(id)
        FROM survey_questions
        WHERE survey_id = 18
        GROUP BY competence_id
    )
    LIMIT 2
);

### Explanation:
1. **Inner Query**:
– Finds the `MIN(id)` for each `competence_id` within `survey_id = 18`.

2. **Intermediate Query**:
– Selects distinct `competence_id` values based on the result of the inner query.

3. **Outer Query**:
– Fetches all `id` values where the `competence_id` is in the result of the intermediate query.
– `GROUP_CONCAT` concatenates these IDs into a single comma-separated string.

### Laravel Query Builder
Here's how you can achieve this using Laravel:

use IlluminateSupportFacadesDB;

// Get distinct competence IDs
$competenceIds = DB::table('survey_questions')
    ->select('competence_id')
    ->whereIn('id', function ($query) {
        $query->selectRaw('MIN(id)')
              ->from('survey_questions')
              ->where('survey_id', 18)
              ->groupBy('competence_id');
    })
    ->distinct()
    ->limit(2)
    ->pluck('competence_id');

// Get all IDs related to those competence IDs
$ids = DB::table('survey_questions')
    ->whereIn('competence_id', $competenceIds)
    ->pluck('id')
    ->implode(',');

echo "Concatenated IDs: " . $ids;

### Example Data

Given a `survey_questions` table:

| id | competence_id | survey_id |
|—–|—————|———–|
| 1 | 101 | 18 |
| 2 | 102 | 18 |
| 3 | 101 | 18 |
| 4 | 103 | 18 |
| 5 | 102 | 19 |

**Step 1**: Inner query retrieves:

| competence_id |
|—————|
| 101 |
| 102 |

**Step 2**: Outer query fetches all `id`s for `competence_id IN (101, 102)`:

| id |
|—–|
| 1 |
| 3 |
| 2 |

**Result**:

Concatenated IDs: 1,3,2

### Laravel Query

use IlluminateSupportFacadesDB;

$competenceIds = DB::table('survey_questions')
    ->distinct()
    ->where('survey_id', 18)
    ->limit(2)
    ->pluck('competence_id');

print_r($competenceIds);

### Explanation:
1. **`distinct()`**:
– Ensures only unique `competence_id` values are selected.

2. **`where`**:
– Adds the condition `survey_id = 18`.

3. **`limit()`**:
– Limits the results to 2 rows.

4. **`pluck('competence_id')`**:
– Retrieves only the `competence_id` column values as a collection.

### Output:
If the `survey_questions` table contains the following data:

| competence_id | survey_id |
|—————|———–|
| 101 | 18 |
| 102 | 18 |
| 101 | 18 |
| 103 | 18 |

The output will be:

IlluminateSupportCollection {#1234
    all: [
        101,
        102,
    ],
}

### Laravel Query

use IlluminateSupportFacadesDB;

$ids = DB::table('survey_questions')
    ->where('competence_id', 71)
    ->pluck('id');

print_r($ids);

### Explanation:
1. **`where('competence_id', 71)`**:
– Adds the condition to filter rows where `competence_id` is `71`.

2. **`pluck('id')`**:
– Retrieves only the `id` column values as a collection.

### Example Output
If the `survey_questions` table contains:

| id | competence_id |
|—–|—————|
| 1 | 71 |
| 2 | 72 |
| 3 | 71 |

The output will be:

IlluminateSupportCollection {#1234
    all: [
        1,
        3,
    ],
}

—

### 1. **Using `pointer-events: none` in CSS**
You can disable the link interaction with CSS by setting `pointer-events` to `none` and optionally styling it differently to indicate it's disabled.

<a href="https://example.com" class="disabled-link">Click Me</a>

<style>
.disabled-link {
    pointer-events: none;
    color: gray;
    text-decoration: none;
    cursor: default;
}
</style>

—

### 2. **Using `href="#"` with JavaScript to Prevent Default Behavior**
You can prevent the link's default behavior using JavaScript:

<a href="#" onclick="return false;">Click Me</a>

Alternatively, if you want to disable the link conditionally:

<a href="https://example.com" id="my-link">Click Me</a>

<script>
document.getElementById('my-link').addEventListener('click', function(event) {
    event.preventDefault(); // Disables the link
});
</script>

—

### 3. **Removing the `href` Attribute**
Removing the `href` attribute from an anchor tag makes it non-clickable.

<a>Click Me</a>

—

### 4. **Disabling with `aria-disabled` for Accessibility**
To improve accessibility, use the `aria-disabled` attribute. Optionally, combine it with JavaScript to prevent the default action.

<a href="https://example.com" aria-disabled="true" class="disabled-link">Click Me</a>

<script>
document.querySelector('a[aria-disabled="true"]').addEventListener('click', function(event) {
    event.preventDefault(); // Prevent action for disabled links
});
</script>

**CSS for better visual representation**:

a[aria-disabled="true"] {
    pointer-events: none;
    color: gray;
    cursor: default;
    text-decoration: none;
}

—

### 5. **Using a `button` Instead of a Link**
If the action does not navigate to another page, consider using a “ instead of a link.

<button disabled>Click Me</button>

—

Choose the method that best fits your use case. For accessibility and clarity, using `aria-disabled` combined with visual cues is recommended.

—

### 1. **Prevent Default Behavior with `event.preventDefault()`**
This is the most common way to disable a link:

<a href="https://example.com" id="my-link">Click Me</a>

<script src="https://code.jquery.com/jquery-3.6.0.min.js"></script>
<script>
    $('#my-link').on('click', function(e) {
        e.preventDefault(); // Prevents the default action
        alert('This link is disabled.');
    });
</script>

—

### 2. **Add `pointer-events: none` Using jQuery**
You can disable the link by applying `pointer-events: none` via jQuery.

<a href="https://example.com" id="my-link" class="disabled">Click Me</a>

<script src="https://code.jquery.com/jquery-3.6.0.min.js"></script>
<script>
    $('#my-link').css('pointer-events', 'none').css('color', 'gray');
</script>

—

### 3. **Using `removeAttr('href')`**
You can remove the `href` attribute from the link, making it unclickable.

<a href="https://example.com" id="my-link">Click Me</a>

<script src="https://code.jquery.com/jquery-3.6.0.min.js"></script>
<script>
    $('#my-link').removeAttr('href').css('color', 'gray').css('cursor', 'default');
</script>

—

### 4. **Conditionally Disable with a Custom Attribute**
You can add a custom attribute like `data-disabled` and check its value to determine whether to disable the link.

<a href="https://example.com" id="my-link" data-disabled="true">Click Me</a>

<script src="https://code.jquery.com/jquery-3.6.0.min.js"></script>
<script>
    $('#my-link').on('click', function(e) {
        if ($(this).data('disabled') === true) {
            e.preventDefault();
            alert('This link is disabled.');
        }
    });
</script>

—

### 5. **Disable Multiple Links at Once**
If you want to disable multiple links at once, you can use a class selector:

<a href="https://example1.com" class="disable-link">Link 1</a>
<a href="https://example2.com" class="disable-link">Link 2</a>

<script src="https://code.jquery.com/jquery-3.6.0.min.js"></script>
<script>
    $('.disable-link').on('click', function(e) {
        e.preventDefault(); // Disable all links with this class
        alert('This link is disabled.');
    });
</script>

—

### Choosing the Best Approach
– **For a temporary disable:** Use `event.preventDefault()`.
– **For permanent disable:** Use `pointer-events: none` or `removeAttr('href')`.
– **For accessibility:** Use a combination of `aria-disabled` and `event.preventDefault()` to signal the link is disabled visually and functionally.

<button id="my-button" class="btn-link">Go to Example</button>

<script>
    document.getElementById('my-button').addEventListener('click', function() {
        window.open('https://example.com', '_blank');
    });
</script>

<style>
/* Style the button to look like a link */
.btn-link {
    background: none;
    color: blue;
    border: none;
    padding: 0;
    text-decoration: underline;
    cursor: pointer;
}
.btn-link:hover {
    color: darkblue;
}
</style>

### Explanation
1. **`window.open()`**:
– Opens the specified URL (`https://example.com`) in a new tab (`_blank`).

2. **Styled as a Link**:
– The button is styled using CSS to appear as a clickable link, with underline and hover effects.

3. **Advantages**:
– This method keeps the semantic meaning of a button while mimicking the appearance and behavior of a link.

### Output
When the button is clicked, it will open `https://example.com` in a new tab.