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substr usage in oracle

substr usage in oracle

The SUBSTR function in Oracle extracts a specific number of characters from a string. The syntax is SUBSTR(string, start_position, length), where string is the target string, start_position is the starting extraction position (starting from 1), and length is the number of characters extracted. A negative starting position means counting down from the end of the string, and omitting the length parameter extracts all characters from the starting position to the end of the string.

May 03, 2024 am 12:00 AM
oracle
Instr usage in oracle

Instr usage in oracle

The function of the INSTR function in Oracle is to find the starting position of a substring in a string. The syntax is INSTR(string, substring, [start_position]). It returns the starting position of the matching substring. If it is not found, it returns 0. Among them, string is the string to be searched, substring is the substring to be found, and start_position is the starting position of the search (optional). The INSTR function is not case-sensitive. By default, it searches from the beginning of the string. It supports searching from the specified position. If the substring appears multiple times in the string, only the starting position of the first matching item will be returned. If the string or subword

May 02, 2024 pm 11:54 PM
oracle
How to use insert in oracle

How to use insert in oracle

The INSERT statement in Oracle is used to insert new rows into the table. The syntax is: INSERT INTO table_name (column1, column2, ...) VALUES (value1, value2, ...), where table_name is the table name, column1, column2, ... is the column name, value1, value2, ... are values. Multiple rows can be inserted. NULL values ​​must be inserted. The values ​​must be compatible with the data type. Repeated primary key values ​​cannot be inserted. The defined trigger will be triggered. If not Specifying column names will insert them in table column order.

May 02, 2024 pm 11:54 PM
oracle
How to use if function in oracle

How to use if function in oracle

The IF function in Oracle is a control flow function used to execute blocks of code based on conditions. Its syntax is as follows: IF (condition) THEN -- If the condition is true, execute this code block ELSE -- If the condition is false, execute this code block END IF;

May 02, 2024 pm 11:54 PM
oracle
How to write when and then in oracle

How to write when and then in oracle

In Oracle, the WHEN and THEN syntax is used in CASE expressions to return different values ​​based on a condition: The WHEN clause specifies the condition to be evaluated. The THEN clause specifies the value to be returned if the condition is true. The ELSE clause (optional) specifies the value returned when all WHEN conditions are false.

May 02, 2024 pm 11:51 PM
oracle
Usage of lag (function and lead (function) in oracle

Usage of lag (function and lead (function) in oracle

The LAG() and LEAD() functions in Oracle obtain the value of the row before (LAG()) or after (LEAD()) the specified row offset from the current row. They are used to analyze time series data and calculate moving averages. The LAG() function returns the value of the previous row, and the LEAD() function returns the value of the subsequent row. The offset can be positive or negative, and returns a default value if it is outside the table range.

May 02, 2024 pm 11:51 PM
oracle
count usage in oracle

count usage in oracle

The COUNT function is used to count the number of rows in the table that meet the conditions. Syntax: COUNT(DISTINCT|ALL expression); where: DISTINCT counts unique values, ALL counts all values. Usage includes counting the number of all rows, the number of non-null values ​​in a specific column, the number of rows that meet the condition, and the number of unique values.

May 02, 2024 pm 11:48 PM
oracle 聚合函数
The difference between concat function and || in oracle

The difference between concat function and || in oracle

CONCAT and || are both string connection functions in Oracle. The main differences are: function syntax (CONCAT with parentheses, || without), NULL processing (CONCAT returns NULL, || returns an empty string), performance (CONCAT is more Slow) and usage scenarios (CONCAT is used for multi-string concatenation that may have NULL, || is used for small-string concatenation without NULL).

May 02, 2024 pm 11:48 PM
oracle
How to use concat function in oracle

How to use concat function in oracle

The CONCAT function in Oracle is used to concatenate strings: Concatenate multiple strings: CONCAT(string1, string2, ...) Concatenate strings and column values: CONCAT('text', column name) Concatenate strings using operators: 'string1' || 'string2' || ...Note: If any string is NULL, the result is NULL; up to 254 strings can be concatenated.

May 02, 2024 pm 11:46 PM
oracle
Tochar usage in oracle

Tochar usage in oracle

The TO_CHAR function converts an Oracle expression to a character value, formatting the output to suit your needs. Use a string template (format_mask) to define the format, including text characters, format modifiers, and placeholders. Format masks are case-sensitive, and placeholders require the correct format modifier.

May 02, 2024 pm 11:45 PM
oracle
How to add two decimal points to an integer in Oracle?

How to add two decimal points to an integer in Oracle?

There are two ways to represent integers with two decimal points in Oracle: scientific notation (such as 100 * 10^-2 = 0.01) and the TO_CHAR function (such as TO_CHAR(100, 'fm9999999999990.99') = 0.01).

May 02, 2024 pm 11:42 PM
oracle
How to use case in oracle

How to use case in oracle

The CASE statement in Oracle is a tool for conditional evaluation, its usage includes: specifying the condition to be evaluated (WHEN). The action (THEN) to perform if the condition is true. If all conditions are false, perform the default action (ELSE, optional).

May 02, 2024 pm 11:42 PM
oracle
What does number(10,4) mean in oracle

What does number(10,4) mean in oracle

The NUMBER(10,4) data type in Oracle stores numeric values ​​with a precision of 4 decimal places, ranging from -9999999999.9999 to 9999999999.9999. The maximum length of the integer part is 6 digits, and the maximum length of the decimal part is 4 digits.

May 02, 2024 pm 11:42 PM
oracle
Usage of to_date in oracle

Usage of to_date in oracle

The TO_DATE function in Oracle converts a string to the DATE data type. Syntax: TO_DATE(string, format_mask). format_mask is a placeholder mask that specifies the format of the date and time portion of the string. Placeholders include YYYY (year), MM (month), DD (day), HH (hour), MI (minute), SS (second), FF (billionth of a second). For example, TO_DATE('2023-03-08', 'YYYY-MM-DD') converts "2023-03-08" to DATE.

May 02, 2024 pm 11:40 PM
oracle

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