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Technical Articles

Database

Oracle

What is the difference between double quotes and single quotes in Oracle

Double quotes and single quotes are used to surround string values in Oracle. The main differences are: Purpose: Single quotes are used for string literals, while double quotes are used for database object names, single-quoted literals, and case-sensitive identifiers. Identifier naming: case-insensitive within single quotes, case-sensitive within double quotes. Escape characters: The escape characters must be escaped with backslashes within single quotes, but they do not need to be escaped within double quotes.

May 07, 2024 pm 02:24 PM

oracle

What is the difference between single quotes and double quotes in Oracle

In Oracle, single quotes are mainly used to define string values and identifiers, while double quotes provide functions such as escape character processing, identifier conflict resolution, and string concatenation: Escape character processing: Double quotes allow the use of escape characters, Single quotes cannot. Identifiers: Single quotes are used for object names, double quotes are used for object names that conflict with keywords. String concatenation: Double quotes concatenate strings and the escaped characters they contain, while single quotes only concatenate the string value itself. Comments: Double quotes can be used for inline comments, but single quotes cannot.

May 07, 2024 pm 02:18 PM

oracle

How to express not equal to empty in Oracle

The syntax for not equal to null in Oracle is IS NOT NULL. This operator checks whether a column or variable contains data; values that contain no data or contain an empty string are treated as NULL. Use the IS NOT NULL operator to filter the result set or to ensure that a column or variable is not NULL before inserting or updating.

May 07, 2024 pm 02:12 PM

oracle

How to write not equal in Oracle

The operator used to express inequality in Oracle is "!==", which compares two values and returns a boolean value of whether they are not equal. The syntax is: expression1 != expression2. This operator can also be expressed as "<>" and is used to filter unequal values.

May 07, 2024 pm 02:09 PM

oracle

How to express equal in oracle

In Oracle, the equal sign is represented by a double equal sign (==) and is used to compare expression values. If they are equal, True is returned, otherwise False is returned.

May 07, 2024 pm 02:06 PM

oracle

How to express not equal in Oracle

The inequality operator in Oracle is represented by "<>" and is used to compare whether two values are equal and return TRUE or FALSE. For example, SELECT product_id, product_name FROM products WHERE product_price <> 10 returns products whose price is not equal to 10.

May 07, 2024 pm 02:03 PM

oracle

What does desc mean in oracle

The DESC (DESCRIBE) command describes the structure of a table or view in an Oracle database, providing information about columns, data types, size, nullability, and other details. The specific steps are as follows: Use syntax: DESC table_name; Return information: column name, data type, size, nullability, default value, constraints.

May 07, 2024 pm 02:00 PM

oracle

Usage of any in oracle

ANY in Oracle is used to check if there is a matching record in a subquery. It applies a subquery to each row in a table, returning TRUE or FALSE to indicate whether there is a match. Specific usage includes: checking matching records: determining whether subquery conditions are met. Aggregation query: Calculate the number of records that meet the conditions. WHERE clause in subquery: Specify the conditions in the WHERE clause of the subquery.

May 07, 2024 pm 01:57 PM

oracle

What to use to connect strings in oracle

There are five ways to concatenate strings in Oracle: 1. Plus (+) operator; 2. CONCAT function; 3. || operator (Oracle 12c and later); 4. DBMS_LOB.CONCAT function (LOB data type ); 5. Combine INSTR and SUBSTR functions. Choose the most appropriate method based on your needs.

May 07, 2024 pm 01:51 PM

oracle

Function of select statement in oracle

The SELECT statement retrieves data from an Oracle table. Functions include: Data retrieval: Select data from a column. Column selection: Specify the columns to retrieve or use (*) to retrieve all columns. Calculation: Perform calculations and return results, such as sums or averages. Conditional filtering: Use the WHERE clause to filter results by condition. Sorting: Use the ORDER BY clause to sort the results by column. Grouping: Use the GROUP BY clause to group results by columns and aggregate data. Join: Use the JOIN clause to join data from multiple tables.

May 07, 2024 pm 01:45 PM

oracle

How to write division in oracle

Division operations in Oracle involve two operators: / (division) and MOD (remainder). The division operator / is used to calculate the quotient (floating point number), while the MOD operator is used to calculate the remainder (integer). The choice of operator depends on what is being calculated: / for commercial, MOD for remainder. It should be noted that the divisor cannot be 0, and the result of the MOD operator has the same sign as the divisor and is always a non-negative integer.

May 07, 2024 pm 01:39 PM

oracle

Function to update one column to another column in oracle

Oracle provides the UPDATE() function and a series of other column update functions, including NVL(), COALESCE(), GREATEST(), and LEAST(), for updating one column to the value of another column. First determine the column to be updated, then find the column from which the updated value is to be obtained, and finally write the UPDATE() function to update the column.

May 07, 2024 pm 01:33 PM

oracle

How to find the sum of each department using the sum function in Oracle

The SUM function in Oracle can be used to calculate the sum of a set of numbers. To calculate the sum of each department, you need to: determine the column to be summarized, usually a numeric or decimal type (such as total sales or order quantity); use the GROUP BY clause Group data by department; use the SUM function in a SELECT statement to summarize the values of the columns in each group.

May 07, 2024 pm 01:30 PM

oracle

How to express an integer with two decimal points in Oracle

There are four ways to complete an integer to two decimal places in Oracle: using the TO_CHAR() function, using the LPAD() and SUBSTR() functions, using the TO_NUMBER() and TRUNC() functions, or using the ROUND() function.

May 07, 2024 pm 01:27 PM

oracle