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YN Wiki

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https://yn-wiki.com

A collection of personal learning notes and technical troubleshooting guides covering a wide range of technologies, including Web frontend and backend, Vue, React, JavaScript, HTTP, Oracle, MySQL, Layui, npm, and MyBatis-Plus-Join.

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What's inside YN Wiki

  1. Perform a full refresh of an Oracle Materialized View

    To attempt a recovery from ORA-12034 or to synchronize a materialized view, you can perform a full refresh using the dbms_mview.refresh procedure. Use the 'C' parameter for a complete refresh.
    -- Identify the materialized view name
SELECT mview_name, last_refresh_date, fullrefreshtim, increfreshtim
FROM dba_mview_analysis;

SELECT * FROM user_objects WHERE object_type='MATERIALIZED VIEW';

-- Perform a full refresh (Replace 'MV_NAME' with your actual view name)
EXEC dbms_mview.refresh('MV_NAME', 'C');
EXEC dbms_mview.refresh('MV_NAME');

  2. Perform date arithmetic using the INTERVAL function in Oracle

    Use the INTERVAL keyword to add or subtract specific time durations (days, years, etc.) from a date. This is useful for querying ranges relative to a parameter or the current system date (SYSDATE).
    -- Query records between a parameter date and 2 days in the future
WHERE table.date_column BETWEEN to_date(#{datetime}, 'YYYY-MM-DD HH24:MI:SS')
AND (to_date(#{datetime}, 'YYYY-MM-DD HH24:MI:SS') + INTERVAL '2' DAY)

-- Query records from the last 5 years relative to current system date
SELECT * FROM oe.orders 
WHERE order_date < (SYSDATE - INTERVAL '5' YEAR)

  3. Drop and recreate an Oracle Materialized View

    If a full refresh does not permanently resolve ORA-12034, drop the materialized view and recreate it. When recreating, ensure you include the rowid if using REFRESH FAST ON COMMIT to maintain performance and synchronization.
    -- Drop the existing materialized view
DROP MATERIALIZED VIEW MV_FORCE_READ_CONTENT;

-- Recreate the materialized view
CREATE MATERIALIZED VIEW MV_CMS_FORCE_READ_CONTENT
REFRESH FAST ON COMMIT
AS
SELECT rowid as rid, VALID_DATE, CONTENT_ID 
FROM dd.user_table 
WHERE VALIDITY = 'VALID';

  4. Refresh an Oracle Materialized View

    To resolve synchronization issues or update data in a materialized view, you can perform a full refresh using the DBMS_MVIEW.REFRESH procedure. First, identify the materialized view name using dba_mview_analysis or user_objects.
    -- Find the materialized view name
SELECT mview_name, last_refresh_date, fullrefreshtim, increfreshtim
FROM dba_mview_analysis;

SELECT * FROM user_objects WHERE object_type='MATERIALIZED VIEW';

-- Perform a full refresh ('C' stands for Complete refresh)
EXEC dbms_mview.refresh('MV_FORCE_READ_CONTENT', 'C');
-- Or a standard refresh
EXEC dbms_mview.refresh('MV_FORCE_READ_CONTENT');

  5. Perform date arithmetic using the INTERVAL function in Oracle

    The INTERVAL function allows you to add or subtract specific time durations (days, years, etc.) from a date. This is useful for querying records within a specific range relative to a parameter or the current system date (SYSDATE). Note that the numeric value in the interval string typically supports up to two digits.
    -- Query records between a parameter date and 2 days in the future
WHERE table.column BETWEEN to_date(#{datetime}, 'YYYY-MM-DD HH24:MI:SS')
AND (to_date(#{datetime}, 'YYYY-MM-DD HH24:MI:SS') + INTERVAL '2' DAY)

-- Query records from the previous X days
-- Use INTERVAL '-X' DAY

-- Query orders from the last 5 years using SYSDATE
SELECT * FROM oe.orders 
WHERE order_date < (SYSDATE - INTERVAL '5' YEAR)

  6. Retrieve values from Layui form fields

    Form field values can be retrieved using standard DOM methods or jQuery if available in the project.
    // Method 1: Direct DOM access
var validEndDateInput = document.getElementById('validEndDate');
var endDateValue = validEndDateInput.value;

// Method 2: Using jQuery
var endDateValue = $('#validEndDate').val();

  7. Format date fields for Layui Table via Java backend

    Alternatively, you can handle date formatting on the backend before sending the data to the frontend. In Java, use the @JsonFormat annotation from the Jackson library on the Date field to specify the desired pattern.
    import com.fasterxml.jackson.annotation.JsonFormat;

@JsonFormat(pattern = "yyyy-MM-dd")
private Date cDate;

  8. Define custom validation rules for Layui forms

    Custom validation rules are defined using form.verify(). Assign the rule name to the lay-verify attribute of the input element.
    <input type="text" name="schoolName" class="layui-input" lay-verify="rule2">
    form.verify({
    rule1 : function(value){
        if (value.length > 250) {
            return '最多输入250字'; // Max 250 characters
        }
    },
    rule2 : function(value){
        if(value.length < 1){
            return '不能为空,请选择'; // Cannot be empty
        }
    }
});

  9. Fix 'npm ERR! could not determine executable to run' error

    If you encounter the error 'npm ERR! could not determine executable to run' within a project, you can resolve it by removing the Git hooks and reinstalling the project dependencies.
    # Remove all files in the .git/hooks directory
rm -rf .git/hooks

# Reinstall dependencies
npm install

  10. Manage permissions for creating Materialized Views

    If you encounter error ORA-01031 (insufficient privileges) while creating a materialized view, you must grant the CREATE MATERIALIZED VIEW privilege to the user.
    -- Check who has the privilege
SELECT * FROM DBA_SYS_PRIVS WHERE PRIVILEGE = 'CREATE MATERIALIZED VIEW';

-- Grant the privilege to a specific user
GRANT CREATE MATERIALIZED VIEW TO username;

  11. Fix 'npm ERR! could not determine executable to run' error

    If you encounter the error npm ERR! could not determine executable to run within a project, you can resolve it by removing the Git hooks and reinstalling the project dependencies.
    # 1. Remove all files in the .git/hooks directory
rm -rf .git/hooks

# 2. Reinstall dependencies
npm install

  12. Manage permissions for creating Materialized Views

    If you encounter ORA-01031: insufficient privileges while creating a materialized view, you must grant the CREATE MATERIALIZED VIEW privilege to the user.
    -- Check which users have the privilege
SELECT * FROM DBA_SYS_PRIVS WHERE PRIVILEGE = 'CREATE MATERIALIZED VIEW';

-- Grant the privilege to a specific user
GRANT CREATE MATERIALIZED VIEW TO username;